Practical 
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Charles E.Foote 




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COPYRIGHT DEPOSE 



PRACTICAL 
ROAD BUILDING 



BY 

CHARLES E. FOOTE 

ENDORSED BY 

The National Highways Association 

AND 

The American Automobile Association 



PHILADELPHIA 

DAVID McKAY, Publisher 

604-608 S. Washington Square 



TE 145" 



Copyright, 1917, by David McKay 



iff-, 

JUN 30 1917 



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CONTENTS 



PART I 
CHAPTER I 



PAGE 

A Sketch of Road History 11 

Early Roads: Babylonian, Egyptian, Persian, Cartha- 
ginian, Greek, Roman. — The Appian Way. — "Crossing 
the Rubicon." — The Dark Ages. — Revival of Civiliza- 
tion. — Highways in France Under Tresaguet. — The 
French Revolution. McAdam and Telford. — The Old 
National Road. — Modern State Aid in the United 
States. 

CHAPTER II 
Road Location 31 

Agricultural, Residential, and Scenic Roads. — Grouping 
and Blending. — Accessibility. — Expense. — Connection 
of Grade and Location. — Permanent Economy. — En- 
hanced Values. — Through Routes. — Line of Sight. — 
Permanency and Value of Correct Location. 

CHAPTER III 

Road Grades 50 

Maximum and Minimum. — Tractive Power. — Direction 
of Loads. — Relation to Surface. — Curves. — »Road Bed. 
— Excavation and Fill. — Side Slopes. — Well-balanced 
Equipment. — Economic Working. 

iii 



IV CONTENTS 

CHAPTER IV PAGE 

Road Drainage 68 

Surface Water. — Crown of Road. — Shoulders. — Side 
Ditches. — Storm Water. — Culverts. — Back Ditches. — 
Sub-drainage. — Climatic Conditions. — Soils. — Concrete 
and Vitrified Pipe. — Drain Grades. — Outlets. 

CHAPTER V 

Road Foundations 88 

Natural and Artificial. — Distribution of Pressure. — 
Carrying Capacity. — Gravels. — Rocks. — Different 
Earths. — Quicksand. — Sinkholes. — Muck. — Swamps. — 
Gettysburg Roads. — Telford. — Concrete. — Old Mac- 
adam. — Bituminous Concrete. 

CHAPTER VI 
Road Surfaces 110 

Grade and Traction Power. — Asphaltic Coating. — 
Steel Tire and Automobile Effects. — Replacement. — 
Relation of Cost of Repairs and Renewal. — Dust Sup- 
pression. — Experiments. — Water Sprinkling. — Oils and 
Tars. — Hot and Cold Asphaltic Oils. — Experimental 
Cost Table. 

CHAPTER VII 

Road Bridges and Culverts 128 

Flow of Water. — Size of Waterway. — Pipe, Box and 
Arch Culverts. — Collapsible Forms. — Face and Wing 
Walls. — Stone Arch Bridges. — Wood, Iron, Steel, and 
Concrete. — Standard Sizes. — Long Spans. — Short-span 
Concrete. — Floors. — Bridge Foundations. 

CHAPTER VIII 
Road Traffic 150 

Traffic Census in France. — England. — Massachusetts. — 



CONTENTS V 

PAGE 

Illinois. — Classification. — Weight and Number of Ve- 
hicles. — Regulations as to Load and Width of Tire. 

CHAPTER IX 

Road Finance 161 

Getting the Money. — Taxation. — Contributions. — 
Sinking Fund, Serial and Annuity Bonds. — Determining 
Comparative Cost. — Enhanced Values. — Spending the 
Money. — Relation of Cost of Repairs to Cost of New 
Improvement. — Specifications, Open, Closed, Alternate. 
— State and Federal Aid. 

PART II 

CHAPTER X 
Earth Roads 175 

Importance of Improvement. — Width. — Crown. — Align- 
ment. — Methods of Improving. — Time to Improve. — 
Grade and Crown on Curves. — Removal of Sod and 
Vegetation. — Preparing and Protecting Side Slopes. — 
Summary. — Maintenance and Repairs. 

CHAPTER XI 

Gravel Roads 195 

Wide-spread Deposits. — Cementitious or Coated Gravel. 
— Washed Gravel. — Subgrade. — One and Two Courses. 
— Old Foundations. — Grading and Screening. — Placing. 
— Rolling. 

CHAPTER XII 

Sand-clay Roads 204 

Theory. — Practical Application. — Different Kinds of 
Clay and Sand. — Chemical Composition of Clay. — 
Proportions. — Building on Sand Subsoil; on Clay Sub- 
soil. — Crown. : — Maintenance. — Natural Sand-clay Mix- 
ture. 



VI CONTENTS 

CHAPTER XIII PAGE 

Top Soil Roads 211 

Character of Suitable Top Soil. — Development. — Rever- 
sal of Accepted Principles. — Reference to University of 
Georgia. — Depth of Material on Road. — Method of 
Construction. 

CHAPTER XIV 

Macadam Roads 215 

Tresaguet. — McAdam. — Standard Construction for 
Years. — Destruction by Combined Automobile and 
Steel Tire Traffic— Width.— Subgrade — Methods of 
Construction. — One and Two Course. — With Telford 
Base. — Weights and Grades of Stone. — Tables. — Re- 
pairing. — Bituminous Macadam by Penetration. — 
Coating. — Maintenance. 

CHAPTER XV 

Brick Roads 235 

Not "Cheap." — Variance in Brick. — Tests; Rattler, 
Absorption, Cross-breaking. — Size. — Quality. — Wire- 
cut-lug and Repressed. — Foundations. — Curb. — Sand 
Cushion. — Filler. — Expansion Joints. — Brick on Sand. 
— A New Departure. 

CHAPTER XVI 

Concrete Roads 249 

Development. — One and Two Course. — Forms. — Shape 
and Character of Subgrade. — Proportions of Mix. — 
Mixing and Placing. — Finishing. — Expansion Joints. — 
Thickness of Concrete. — Covering. — Cracks and Treat- 
ment. 

CHAPTER XVII 

Bituminous Roads 261 

Development from Experiments. — Penetration and 
Mixing Methods. — Asphaltic Concrete. — Foundations 



CONTENTS Vll 

PAGE 

for. — Mixing Plants. — Mineral Aggregate. — Heating 
Materials. — Spreading and Rolling. — Seal Coat. — Dif- 
ferences in Asphalts. — Specifications and Bids. — Guar- 
antees. 

CHAPTER XVIII 

Sand-asphalt Roads 281 

The Cape Cod Road. — Special Construction in Florida 
by Hotel Proprietor. — Further Experiments. — Possible 
and Probable Future. 

CHAPTER XIX 

Special Surface Roads 286 

Amiesite. — Burnt Clay. — Hassam. — Shells. — Other 
Types with Which Local Experiments Have Been 
Made. — Variety of Inventions. 



ILLUSTRATIONS 



GURE PAGE 

1. Road Winding Among the Hills 35 

2. Road Cut Into Base of Mountain 41 

3. Practical and Simple Method of Establishing a Curve 45 

4. A Long Side-hill Grade in Ohio 55 

5. Method of Determining the Grade of a Road 57 

6. Loose Stone Under-drains Below Side Ditches 71 

7. Roadway Drains Itself 72 

8. Culvert Under Side-hill Road 72 

9. Plan of Drainage in a Cut 73 

10. Drainage Model 86 

11. Stone Foundation Forming V-drain 97 

12. A Concrete Bridge in Florida 141 

13. Illinois Short Span Bridge 142 

14. Concrete Pile and Slab Bridge 143 

15. Concrete Girder Bridge 144 

16. Type of "Sectional" Bridge 145 

17. Shape of Earth or Gravel Road 182 

18. Well Shaped and Graded Earth Road 185 

19. A Gravel Road in New York State 199 

20. A Sand-clay Road in Florida 207 

21. Top-soil Road in Alabama 213 

22. Rolling Subgrade for Macadam 218 

23. Rolling Lower Course of Stone 219 

24. Completed Macadam Road (New York) 220 

25. Completed Macadam Road (Ohio) 221 

26. Brick Road in Florida 239 

ix 



X ILLUSTRATIONS 

FIGURE PAGE 

27. Brick Road in Ohio 242 

28. Depositing Concrete on Road 252 

29. Finishing Concrete Road Surface 253 

30. Completed Concrete Road 254 

31. Portable Asphalt Plant 267 

32. Dumping and Spreading Asphaltic Concrete 268 

33. Applying Seal Coat with Machine 269 

34. Covering Seal Coat 270 

35. Chevy Chase Road (Asphaltic Concrete) 271 

36. Laying Sand Asphalt 282 

37. Sand Asphalt Road 283 

38. Amiesite State Road in Pennsylvania 287 

39. Preparing for Burnt Clay Road 289 

40. Shell Road in Louisiana 293 



PREFACE 



The call for a book on "Practical Road Building" 
reached the author from a variety of different sources 
during the past three or four years. The most im- 
pressive of these came from personal experiences when 
delivering lectures in various sections of the country on 
"Highway Construction/' "Highway Bonds," "Road 
Materials," and other phases of the Road Industry, 
when farmers, bankers, merchants, local officials, local 
capitalists, local producers, and local vendors sub- 
mitted questions readily answerable except for the 
limit of time. 

"Where can the information be obtained in concrete 
and intelligible form?" was the final question. And as 
it could not be answered, this volume is intended to 
meet the requirements. 

The Federal Office of Public Roads and Rural Engi- 
neering readily supplies information concerning any 
detail. A number of technical works on Highway 
Engineering are of the highest excellence; a multitude 
of papers and addresses, read and delivered at various 

xi 



Xll PREFACE 

Highway and Engineering Conventions, and the reports 
of various committees of technical societies, all contain 
information of great value, but which is unavailable to 
the lay reader — the average local official and the citizen 
— because of their technical character and form of ex- 
pression. 

In this volume the fullest possible use has been made 
of all such technical information as would fit the condi- 
tions, and the author desires to express his fullest ap- 
preciation and to extend the greatest possible credit to 
those from whose works he has abstracted information 
and turned it into practical and intelligible language for 
non-technical readers. To give the names of those 
whose writings have been in part appropriated would be 
to prepare a list of all the men prominent in the Road 
Industry during the last ten years; a list too long for 
these pages. 

The fact that the great State and Federal appropria- 
tions for improved roads will apply mostly to main 
roads, which will be in charge of presumably competent 
highway engineers, does not alter the fact that fully 80 
per cent, of the roads of the country will for many years 
remain in the hands of local officials and be subject to 
the influences of local necessities and local sentiment. 
While many engineers may gain knowledge and in- 
formation from these pages by careful study, the pri- 
mary purpose of the author has been to present a work 



PREFACE Xlll 

which will give full information to the reader who wants 
it presented in plain language without technicalities. 

The closing months of 1916 emphasized the necessity 
for road improvement in the United States more forcibly 
than any other period during two generations of men. 
The cost of primary marketing; the difficulties of prompt 
transportation, and the excessive prices at points of 
consumption have made a community of interest be- 
tween the producer and ultimate consumer which should 
go far to show their interdependence on each other, and 
their mutual interest in the reduction of primary trans- 
portation expense by means of improved highways. 

The destinies of the Nation depend on the conserva- 
tion of its resources. In no one direction in the past 
has there been more waste than that caused by bad 
roads. If the information presented in these pages 
shall to any considerable extent add to the intelligent 
extension of country road building with the consequent 
advantages to the communities, States, and Nation, 
the author will consider that the work involved in its 
preparation has been of value to the people of the 
country. 

Chas. E. Foote. 

New York, 
January 1, 1917. 



FOREWORD 




ROADS AND THE ROAD USER 

With over 3,500,000 automobiles in use in the 
United States, or an average of 1 for every 29 people, 
it is only natural that there should be the widest in- 
terest among motorists in the improvement, construc- 
tion, and maintenance of public highways. It is alto- 
gether probable that the ultimate number of automo- 
biles will be double the number now in use. 

It is estimated that the investment in automobiles 
now is $3,000,000,000, and that the ultimate invest- 
ment will be $6,000,000,000. It has been estimated 
that the average distance that each automobile is 
driven yearly is 4000 miles, which would make the 
staggering total of over 14,000,000,000 car miles every 
twelve months, with an ultimate of probably 
28,000,000,000 car miles. The average annual cost of 
operating an automobile is $250, which would make a 
total annual operating charge of $878,000,000, or an 
ultimate of $1,757,000,000. 

xv 



XVI FOREWORD 

In view of these figures, it is not astonishing that the 
average motorist should appreciate the necessity of 
larger expenditures than ever before for road im- 
provements. 

Road improvement is as necessary, from the stand- 
point of the motorist, as gasoline, oil, tires, and car 
repairs. A certain part of such cost must be assumed in 
computing automobile expense. Improper construc- 
tion and inadequate maintenance are not only a source 
of annoyance and inconvenience to the motorist, but 
are just as much a source of expense as a poor quality 
of gasoline or improperly built tires. 

The motorist constantly passes over city and town- 
ship lines, goes from one municipal subdivision to an- 
other, so he desires smoothly paved city and village 
streets as well as improved country roads. The pre- 
ponderating percentage of good roads are built — 
In Cities, through their departments of public works, 
In Parks, by the commissioners in charge, 
In Villages, by local street commissioners, 
In Townships, by township boards and highway com- 
missioners, 
In Counties, by county commissioners, or super- 
visors, 
In States, through state highway commissioners, 
In the Nation, pursuant to the recently enacted 
Federal Aid Road Act. 



FOREWORD XV11 

The improvement of city streets and park boulevards 
are of ever-increasing importance, yet the greatest 
mileage of through-roads must be constructed in the 
rural localities in whole or in part by the four political 
subdivisions, viz.: the Town, County, State, and 
Nation. 

The permanent roads outside of cities and villages in 
New York State, upon the completion of the proposed 
systems, will represent a capital investment of 
$300,000,000, or about equal to the amount invested 
in automobiles. There are 80,000 miles of highway in 
that commonwealth, so the average capital investment 
is about $3750 per mile of highway. 

There are approximately 2,000,000 miles of highway 
in the United States. At $3750 per mile, this would 
represent a capital investment of $7,500,000,000. 
The ultimate value of automobiles will be upward of 
$6,000,000,000. 

The maintenance, reconstruction, and upkeep will 
represent possibly 5 per cent, of the capital on 
$375,000,000, about one-quarter of the ultimate auto- 
mobile operating charge. 

The preparation of road plans, the selection of types 
of construction, and the various details must be deter- 
mined by competent highway engineers, appointed on 
merit and assured of a reasonable tenure in office. 

All of the several types of road described in this 



XV111 FOREWORD 

volume have their place in one or another of the classes 

of improvement. There is no type of road which is 

applicable to all classes, and any work which adds to 

the popular knowledge of this subject is of value. It 

is with this purpose that the American Automobile 

Association endorses this volume, which presents many 

interesting road matters in a form to be appreciated 

by the average motorist. 

George C. Diehl, 
Chairman A. A. A. Good Roads Board. 
Washington, D. C, 
May, 1917. 



FOREWORD 




The title of this book, "Practical Road Building," 
carries with it the author's purpose. Not a technical 
treatise for engineers or scientists, and yet an engineer- 
ing book for the road builder who is called upon to 
build and who must build, and at once, with but little 
if any scientific education himself or the means of its 
employment. And yet also a book full of valuable 
practical information for the engineer himself, and 
stated in common-sense language devoid of hair-split- 
ting, technical nomenclature. 

There are many thousands of road officials in our 
small towns, villages, townships, and counties who will 
find it easy of reading and understanding and valuable 
in its shortness, simplicity, and directness of statement 
and purpose. It appeals more directly to the practical 
lay mind, and yet has great value to the average engi- 



XIX 



XX FOREWORD 

neer as well. The author, Mr. Charles E. Foote, has 
for many years devoted himself to the practical side 
of road improvement. He is well qualified by his 
knowledge and experience as a writer to set forth the 
subject from its practical viewpoint. 

In appreciation of the wide general value of such 
treatment of the subject the National Highways Asso- 
ciation has endorsed this volume as the first of a series. 
Others on "Road Machinery" and "Highway Mate- 
rials" will follow, largely through the interest and co- 
operation of David McKay, the publisher, whose ex- 
ceptional facilities for their distribution should give 
this volume, and those following, a large National 
audience. This is the hope and wish of the National 
Highways Association. 

Charles Henry Davis, C. E., 

President National Highways Association. 




PRACTICAL ROAD RUILDING 



PART I 

CHAPTER I 

A SKETCH OF ROAD HISTORY 

The most insistent demand made by civilization at 
the beginning of the twentieth century is for better 
means of communication; that communities and 
peoples may keep in closer touch with one another; 
that commerce may become more and more liquefied; 
that social and moral welfare may be enhanced, and 
that the people, by reason of this closer contact with 
each other, may keep up with the spirit of the age in 
culture and righteousness and wealth. To accom- 
plish these ends requires the improvement of the pub- 
lic highways. 

From the beginning of civilization history makes 
frequent mention of the building of roads, and in some 
instances modern excavations have disclosed the exist- 
ence of great highways which the historians have 

11 



12 PRACTICAL ROAD BUILDING 

overlooked. As nearly as may be ascertained those 
ancient highways were built for military purposes; for 
the more rapid movement of armies and the transpor- 
tation of munitions of war; but they served the pur- 
pose, also, of channels of commercial and social com- 
munication and in this manner aided in the world's 
intellectual development. 

Nearly four thousand years ago the city of Ancient 
Babylon, the city made famous by the biblical story 
of Belshazzar and the handwriting on the wall, built 
a road to Nineveh, a distance of nearly 400 miles. The 
road was broad and well graded, and was paved with 
brick set in a mortar of asphalt. Sections of this road 
are still found, buried under the accumulations of 
centuries, when the tools of the archaeologist bring them 
once more to the light of day. 

In Egypt, near the Great Pyramids of Gizeh, have 
been found the ruins of a great highway, or causeway, 
more than a mile long. Herodotus mentions that the 
great King Cheops built such a road for the transpor- 
tation of materials used in building the Pyramids. He 
states that the road required the work of 100,000 men 
for a period of ten years. It is probable that the ruins 
recently discovered are a part of the same highway. It 
was built of stone blocks some of which are 10 feet 
thick. Temples, parks, statues, and mausoleums were 
placed along its sides. 



A SKETCH OF ROAD HISTORY 13 

The Persians had a system of military highways 
which extended for long distances throughout that 
country. They maintained a post or messenger ser- 
vice, with stations 18 to 25 miles apart, where messen- 
gers would exchange their tired horses for fresh ones. 
In this way a speed often reaching more than 100 miles 
a day was secured. 

According to the historian Strabo, there were two 
great roads extending between Syria and Babylon. 
One of these was much more popular than the other 
because of the fact that less toll was charged. 

In ancient Greece much attention was devoted to the 
subject of highways by the Senate at Athens and the 
authorities of Thebes and Lacedsemon. Highways 
were maintained to the Piraeus and to the sacred shrines. 

An interesting story comes down in the history of 
Thebes. It appears that Epaminondas, one of the 
greatest of Theban generals, had failed to capture 
Corinth; and as a result had been visited with the indig- 
nation and contempt of the populace. In order to 
express more completely their sentiments toward him 
they elected him to the office of "cleaner of streets," 
which office at that period was the lowest and most 
despised of any occupation in that city. 

As the story goes, Epaminondas accepted the situa- 
tion gracefully, and turned his attention to cleaning the 
streets of Thebes. By virtue of his great ability and 



14 PRACTICAL ROAD BUILDING 

his trained mind he made Thebes the cleanest and most 
beautifully kept city in the world, until its cleanliness 
became proverbial, and was noted in the literature of 
the times. "As clean as Thebes" is still a proverb 
noted in the early Greek classics. Then the office of 
Cleaner of Streets became the highest office within the 
gift of the people, and citizens of the highest standing 
and culture aspired to it. 

Most historians, in commenting on the great Roman 
roads, intimate that the art of road building was learned 
by the Romans during the long series of wars* with 
Carthage. It is known that the Carthagenians had a 
great system of highways, which, together with their 
communication by sea, enabled them to withstand the 
alternate assaults of Greece and Rome for several centu- 
ries. For nearly four hundred years Carthage sustained 
long and bloody wars. It fell about 146 b. c, and about 
all that can be found today of its ancient civilization is 
the ruins of some most excellently built highways. 

In its conquest of the world Rome built twenty-nine 
great highways radiating from the Eternal City into 
the various provinces. It seems to have been the 
policy, as soon as a section or country was conquered, 
to connect it with Rome by a great highway, over which 
troops could be moved with celerity and over which the 
tribute, which Rome always demanded, could be car- 
ried to the Capital. 



A SKETCH OF ROAD HISTORY 15 

One of the most famous of these roads is still known 
as the "Appian Way." It was begun by Appius Clau- 
dius about 312 b. c. and was first built to Capua, about 
142 miles. Later it was continued to Brundisium — 
now Brindisi — making its total length approximately 
360 miles. It is supposed to have been completed dur- 
ing the reign of Julius Caesar. The Roman roads were 
of very heavy construction, and similar roads today in 
the United States would cost approximately $245,000 
per mile. 

We learned in our early Latin studies that when 
Caesar started out with his legions for the conquest of 
Gaul he "crossed the Rubicon" and "burned his 
bridges behind him." These facts have been paraded 
to an admiring world for twenty centuries as the high- 
est possible examples of patriotism and determination. 
They have carried the idea that there was no possibil- 
ity of turning back, and that the means of retreat had 
been destroyed, that such a temptation should not 
occur. 

Yet, when we study the progress of that campaign of 
conquest through France and Belgium and into Britain 
the fact is borne in on us that Caesar must have been 
making what would now be called a "grand-stand play," 
or perhaps "playing to the galleries," because, as a 
matter of fact, Caesar had among his forces a set of the 
most expert bridge builders in the then known world. 



16 PRACTICAL ROAD BUILDING 

Specimens of their handiwork are still extant in struc- 
tures of masonry which are still doing service on the 
highways of France and Britain, where great roads 
were built by the invading Roman hosts. 

It seems very probable that none of the ancients 
really appreciated the commercial value of their high- 
ways. The periods were periods of wars and military 
operations, and the transportation of troops and sup- 
plies was the paramount necessity. This aspect is 
confirmed by the fact that after the fall of Rome, and 
during that period of history known as the "Dark 
Ages" extending down to the ninth or tenth century, 
when practically all Europe relapsed into feudalism, 
thousands of miles of highways were destroyed and 
bridges torn down, because of the fact that they would 
furnish easier access by enemies. Such civilization as 
there was seems to have found its expression in archi- 
tecture, in the construction of great castles, and in 
making them impregnable. Commerce on land, such 
as there was of it, was mostly carried on on the backs 
of horses. 

By reason of these conditions the association of 
peoples with each other became restricted. Education 
languished and in many regions disappeared, except 
among the religious orders and in some of the most 
highly cultivated families. Many kings and princes 
of those times could neither read nor write. 



A SKETCH OF ROAD HISTORY 17 

Road building, that is, the building of good roads, 
did not soon begin after the human mind had begun to 
throw off the shackles of isolation, and the people again 
began to form combinations for mutual advantage, 
which combinations finally resolved themselves into 
more or less stable governments. Roads were just 
what the people of localities made them. In the 
seventeenth century England passed a law authorizing 
the seizure of land along a highway for the use of travel- 
ers when the road became so deep as to be impassable. 
Contemporaneous history states that the roads of 
England at that day were worn into great trenches, 
sometimes 4 feet deep, in which the water settled 
after rains. At about the same period laws were en- 
acted requiring that the forests be cleared from each 
side of the road to a distance of 200 feet, so as to pre- 
vent surprises to travelers by the highwaymen and 
brigands who at that time had become a menace to 
travel. 

The building of improved highways, as the term is 
understood today, began about 150 years ago in France. 
In 1764 a provincial engineer named Tresaguet, of 
Limoges, who had made a local reputation by building 
roads of broken stone, was called to Paris by King Louis 
XIV to explain his system. He was then appointed by 
the king to the position of Assistant Inspector General 
of the Department of Public Works, in charge of roads 






18 PRACTICAL ROAD BUILDING 

and bridges, and began the construction of a system of 
King's Highways in France. 

In the year 1776, when the American colonies were 
declaring their independence, France adopted as a 
National Highway System the roads previously built, 
and those to be built between the city of Paris and the 
principal cities of the various provinces or depart- 
ments of the country. The work of construction con- 
tinued until about 1790, when 15,000 miles of stone 
roads had been completed. 

For probably one hundred years before the appear- 
ance of Tresaguet spasmodic efforts had been made at 
improving the King's Highways. Several prime min- 
isters, including Richelieu, the " Great Cardinal," had 
made efforts in that direction. Most of the labor, both 
before and during the administration of Tresaguet, was 
forced labor, levied upon the peasantry. Some his- 
torians consider this one of the contributing causes of 
the French Revolution, known as the bloodiest tragedy 
of history. 

Studying the question from a broader and deeper 
and more comprehensive standpoint, it seems that it 
was the facility of communication offered by these 
highways that made the Revolution possible. For 
hundreds of years the peasantry of France had been 
ground under the heel of despotism. By reason of the 
isolation of the various sections from each other there 



A SKETCH OF ROAD HISTORY 19 

could be no common thought or expression. The 
people were sent to work on the roads or drafted into 
the army at the pleasure of their royal masters. 

While the great highways were built for the primary 
purpose of moving troops and supplies, they also af- 
forded the means of communication between the 
people of the different parts of the kingdom, and per- 
mitted the development of that irresistible sentiment 
which caused the population to rise and move, like a 
steadily growing avalanche, on to the capital where the 
great tragedy culminated. 

Later, Napoleon Bonaparte extended the system of 
highways, and had cross-roads built. He also put in 
operation a system of maintaining the roads by putting 
a patrolman on every 5 or 6 miles, and placing materials 
along the roadside, so that any defect in the road sur- 
face could be treated without delay. This system still 
prevails, and has been incorporated into the highway 
systems of most of the countries of Europe and into 
those of several States of the Union. 

The elaboration of the Road System of France by 
Napoleon, primarily for war purposes, had effects which 
may not have been contemplated by him. With the 
National Highways, the Departmental Highways, and 
the Communal Highways surfaced with stone, the 
peasantry became rich — the richest class per capita 
of any farming people on the face of the earth. Educa- 



20 PRACTICAL ROAD BUILDING 

tion and knowledge spread, and the people were 
brought into closer communication with each other. 

Then came the downfall of monarchy in France. Is 
it not fair to assume that the downfall was due to the 
roads which permitted the free interchange of thought 
throughout the country? That the highways which 
had been designed as an aid to national defense and 
offense became also the channels to material wealth, 
and to that higher intelligence which makes absolutism 
in government impossible? 

French roads are today considered the best in the 
world, and its systems are the patterns for the road 
builders of all countries. But the governmental prin- 
ciples under which they were designed have been found 
wanting in the inexorable evolution of time. 

English roads continued in very bad condition from 
earliest historical periods until the appearance of Tel- 
ford in the South of England and in Wales, and 
McAdam in the North of England, about 1815. Tel- 
ford's plan was to take field stones, set them on edge 
with the pointed end up, then break off the points with 
a sledge, and drive the pieces down as wedges to hold 
the stone firmly. On top of this was placed a layer of 
broken stone for a wearing surface. This class of 
foundation is still much used in making road founda- 
tions, especially where the ground is low or marshy. 
McAdam's plan was the original form of what is still 



A SKETCH OF ROAD HISTORY 21 

known as the macadam road. It was made of broken 
stone, which the traffic would pack down. When the 
surfaces of the stones would crumble or be broken off 
into small particles or into dust, the rains would wash 
the smaller particles into the interstices, and further 
traffic would hold them there, and thus a smooth, even, 
hard surface was produced. This method was prac- 
tically identical with that of Tresaguet of fifty years 
previous. 

Early efforts to build roads in the United States met 
with little encouragement. The first road law enacted 
in the colonies, so far as can be ascertained, was by 
Virginia in 1632. The "New England Path," between 
Boston and Plymouth, was begun in 1639. The Prov- 
ince of New York enacted laws regulating the building 
of roads in 1664, and in 1666 Maryland passed a road 
law. In 1692 Pennsylvania enacted a law placing the 
control of the roads in the hands of township officials. 
This was changed to county control in 1700. 

But little seems to have been done with the roads 
for nearly a century, or until after the close of the 
Revolutionary War. The larger cities were all at the 
seaboard, and most of the cultivated farms were along 
or near waiter-courses which could be used for such 
transportation of agricultural products as was found 
necessary. 

Within a few years after the independence of the 



22 PRACTICAL ROAD BUILDING 

colonies, and the formation of stable government for 
the union of States, the necessity for highways became 
insistent. In 1786 Virginia authorized the construction 
of a highway across the Cumberland Mountains into 
Kentucky for the accommodation of the trade of those 
who had settled and were settling that territory; and 
when Kentucky became a State in 1792 one of the very 
early acts of its legislature was to provide for the con- 
tinuation of the highway in the new commonwealth. 

In 1794 was started what is supposed to have been 
the first broken stone road in the United States — the 
Philadelphia and Lancaster Turnpike, in Pennsylvania. 
It was built as a toll road by private capital, and to this 
day most if not all of the road still collects toll from 
those who pass over it. 

The city of Lancaster, Pennsylvania, has a popula- 
tion of about 35,000 people, and is located in what is 
claimed to be the richest agricultural county in the 
United States. But there is no highway by which that 
city can be entered or departed from without paying 
toll. Notwithstanding this fact, in a recent election 
for a state road system the people of the city and 
county gave a majority against good roads of over 11,000 
votes out of a total vote of less than 16,000. In the 
adjacent county of York a similar condition prevails. 

Toll roads, which were common in the early history 
of the country, have almost vanished, and a few more 



A SKETCH OF ROAD HISTORY 23 

years will see their total elimination. They served their 
purpose and served it well. Now, like obsolete factors 
in human progress, they must give way. 

The United States Government went into the road 
building business in 1806, when what was known as 
the National Road was authorized by Congress and 
construction commenced. The original design was to 
build the highway from tidewater on the Atlantic Coast 
to a point on the Mississippi River opposite St. Louis, 
what is now East St. Louis, Illinois. As a matter of 
fact the construction began at Cumberland, Maryland, 
which was practically the head of navigation on the 
Potomac River. The road was built across the slender 
part of the state of Maryland, through the southwestern 
portion of Pennsylvania, and across the panhandle of 
the state of Virginia — now West Virginia — to the 
Ohio River. 

Crossing the Ohio River by ferry, the road took al- 
most a direct line across the states of Ohio and Indiana, 
passing through the capitals, Columbus and Indian- 
apolis, thence deflecting a little to the southwest, 
reached across the state of Illinois. 

Appropriations were made by Congress from time to 
time as the work of construction progressed. The 
engineering work was of the highest order. The road 
was well graded and surfaced with broken stone or 
gravel, mostly under the direct supervision of govern- 



24 PRACTICAL ROAD BUILDING 

merit engineers. The road was completed to the 
Ohio River in 1817, and furnished the main thorough- 
fare between the East and the rapidly growing West. 
Within about twenty years afterward the road had 
been graded throughout its entire length, and the heavy 
stone surface and the bridges of stone masonry had 
been completed as far as Indianapolis. The last con- 
gressional appropriation was made in 1838. 

As illustrating the short-sightedness of many of the 
human family, it is worthy of note that when the 
National Road was proposed, so that stage-coaches and 
freight wagons could be hauled long distances with 
comparative ease, the most violent opposition was en- 
countered. It was held by those opposing the road that 
the then great industry of conveying passengers and 
freight across the mountains from the Potomac to the 
Ohio on horseback would be destroyed, and that thou- 
sands of men would be out of work, and hundreds of 
thousands of dollars' worth of animals and equipment 
be rendered worthless. 

Again, when the railroads began to be built from the 
east to the west, there was the same violent opposition 
from those individuals and statesmen who could see 
only the ruin of the stage-coach and team-freighting 
industry. True, those industries were ruined so far 
as main line traffic was concerned, but the establish- 
ment of better and cheaper means of through transpor- 



A SKETCH OF ROAD HISTORY 25 

tation not only made opportunities for "feeders" which 
required all the existing equipment, but many times 
more. 

While the National Road had been building Ohio and 
Indiana had built thousands of miles of gravel and other 
kinds of improved roads, most of which led to the Na- 
tional Road, though some connected with the Ohio 
River on the south, or with Lake Erie on the north. 

After the beginning of railroad building the National 
Road was virtually abandoned. First, Congress turned 
the various sections of it over to the states in which 
they were located, provided the states would keep them 
in repair. Then the states turned sections over to the 
counties under similar conditions. Then some counties 
established toll-gates to get money for maintenance; 
others turned their sections of the road over to turn- 
pike companies, to collect tolls and maintain the road. 

In the meantime railroads were built, and local roads 
were made to reach their stations. Here and there 
sections of the National Road were abandoned, its mile- 
stones and some of its bridge masonry were appropri- 
ated by the inhabitants for building or other purposes, 
until a score of years ago it was almost impossible to 
find more than half the original route. 

Within the past few years measures have been taken 
to restore the Old National Road. Nearly all of that 
section located in Pennsylvania has been incorporated 



26 PRACTICAL ROAD BUILDING 

in the system of State Highways of that state, and 
special appropriations made for its improvement. In 
Ohio and Indiana Good Roads Associations have taken 
up the matter, and are raising funds for accomplishing 
this result. So it may be that within a short time the 
Old National Road, for which congressional appropria- 
tions reached a total of nearly $7,000,000, will be re- 
stored to its pristine splendor and usefulness; not, to be 
sure, in carrying stage-coaches and trains of freight 
wagons, but for the passage of that modern device for 
consuming distance — the automobile. 

The subject of the National Road should not be left 
until one point is made clear. Reference is always 
made to the fact that the road was built by the Federal 
Government. That is literally true. The appropria- 
tions were made by Congress, and the work was done 
by government officials. But there is another side to 
the case which is not so generally known : 

When Ohio was admitted to the Union as a St^te in 
1802, the law which provided for its admission to the 
Union contained a clause providing that 5 per cent, of 
the money received from the sale of public lands within 
the state should be used for constructing highways. 
Of this three-fifths should be applied to roads within 
the state, and two-fifths to the construction of a high- 
way from the eastern boundary of the state to tide- 
water on the Atlantic Coast. 



A SKETCH OF ROAD HISTORY 27 

When Indiana was admitted about 1816, and Illinois 
at a later date, similar provisions were made; and it has 
not transpired, so far as current history shows, that the 
government of the United States has ever returned to 
those states the balance of the money due them for 
roads under these laws. Possibly if a settlement were 
to be made today, each of these states would find that 
they have enough money coming from the Federal 
Government to build many miles of the highways re- 
quired by modern traffic. 

Since about 1840 until about twenty years ago, a 
period of more than half a century, American civiliza- 
tion busied itself with building railroads. Highways 
were neglected, while twin streaks of steel were built 
into every corner of our great country, affording a de- 
velopment which, in extent of territory covered and the 
number of people permanently located, and the area of 
cultivation opened, has made a new record in the 
history of the world.* So that we have now m the 
United States more miles of railroad than all the rest 
of the world put together. 

While we were building railroads and creating an 
empire the nations of Europe were building highways. 
Now that there is a cessation in railway extension, 
Americans are giving their attention to the building of 
roads, for the comfort and convenience of our people, 
and for the reduction of the cost of transportation of 



28 PRACTICAL ROAD BUILDING 

food-stuffs and other products from the farms where 
they are grown to the market in which they are con- 
sumed, or to the shipping-point whence they are con- 
veyed to such market. 

The modern movement for good roads began in 1891 
in New Jersey, Massachusetts followed in 1894, Con- 
necticut in 1897, New York in 1898. Other states have 
followed until there are now forty-four states in the 
Union either with regularly organized Highway De- 
partments, or with some method arranged for the 
systematic improvement of the highways. 

About a dozen years ago a new factor appeared which 
has had to be reckoned with in the improvement of the 
highways. The factor is the automobile. At the 
beginning of 1904 there were approximately 50,000 of 
them in the entire United States. At the beginning of 
1917 there are nearly 2,800,000 of them on our high- 
ways. 

This is a new traffic superposed on the former traffic, 
as the use of horse-drawn vehicles has declined but 
little if any. The mechanical vehicles form just so 
much added wear on the roads, additional agents of 
destruction. 

The broken stone or macadam roads of our fathers 
and grandfathers, which for a century and a half had 
been considered the highest standard form of construc- 
tion, go to pieces rapidly under the combined travel of 



A SKETCH OF ROAD HISTORY 29 

horse-drawn and motor-driven vehicles. The iron shoes 
of the horses and the steel tires of wagons break up the 
stone surface; then the low-bodied, swift-moving auto- 
mobile comes along, and the dust which formerly was 
packed into the road and made it solid, is sucked out 
and thrown into the air, whence it is wafted away over 
the adjacent fields, injuring the crops and causing dam- 
age and irritation. Then the horses and wagons break 
up more stone, and the automobiles distribute it, and 
presently the whole road is ruined, requiring a new 
surface. 

During the last eight or ten years highway engineers 
have been inventing new styles of road surface, and 
motor engineers have been inventing new and heavier 
styles of vehicles. First one has a little advantage, then 
the other. Motor trucks have grown in weight and 
carrying capacity until they exceed those of the rail- 
road freight cars of a few years ago. When roads are 
built firm and solid enough so that they will stand the 
stress — with heavy foundations and tenacious surface 
— some other and heavier vehicle is invented. In their 
turn have come, in some localities, the auto-omnibus, 
carrying as many as thirty people, making regular trips 
between country towns; and motor freight trains, each 
with a heavily loaded motor truck in front, hauling a 
string of loaded freight wagons behind. 

From other countries come stories of "trackless 



30 PRACTICAL ROAD BUILDING 

trolley lines/' with the wires strung over the highway 
and the cars running on the roadway without rails. 
Where the development of the vehicle is to find its 
limitations, or what the road of the future may be, no 
man can tell. It requires the best intelligence of today 
to design and construct roads which will meet the re- 
quirements of the present. The future must take care 
of itself. 

In this country there is being expended annually 
from $350,000,000 to $400,000,000 for the construction 
and repair of the roads. There are about 2,200,000 
miles of roads in the country, and rural mail carriers 
go over approximately half of them every day, carrying 
knowledge of the world and its affairs to 80,000,000 
people who lived in comparative isolation ten years ago. 

It may be stated that the automobile and the rural 
mail carrier are the two great factors of recent years in 
the demonstration of the necessity for improved roads 
and more of them. 

Good roads mean to a people everything that is good. 
They mean higher standards of morality; better stand- 
ards of thought and action; clearer comprehension of 
the great master-thought which we call nature's God. 
And they mean that freer intercourse which, particu- 
larly in our own country, has inculcated ethics and 
eliminated provincialism throughout the nation. 



CHAPTER II 



ROAD LOCATION 



As the primary purpose of a road is to carry the 
traffic, it naturally follows that its location should be 
such as to accommodate the greatest amount of traffic. 
In classifying roads from the standpoint of location, 
therefore, three distinct groups appear. They are: 

(a) Agricultural. 

(b) Residential. 

(c) Scenic. 

While the roads composing these groups overlap, and 
one group frequently changes or melts into another, the 
subject must be considered from the primary necessities 
of the group itself, and provisions made for harmonious 
blending when two or more groups come together. 

In the greater part of the United States the roads are 
constructed on section lines, one mile apart in each 
direction. When a section of country becomes thickly 
settled and the land is cut up into small farms, roads are 
often built on half-section lines, making parallel roads 
one-half mile apart, and sometimes closer than that. 
These smaller subdivisions usually occur near cities or 
towns, where the district may be given up to suburban 

31 



32 PRACTICAL ROAD BUILDING 

residences or to market-gardening and similar pur- 
poses. In the older states and in hilly and mountain- 
ous regions the roads generally follow the valleys of 
streams, rising gradually to the higher elevations 
through the winding courses formed by nature. 

But the grouping of roads remains practically the 
same. The greater the distance from city or town, the 
larger becomes the average size of farms. The indus- 
tries of the people are more entirely agricultural. At 
the same time, in certain localities, great scenic advan- 
tages may be found which may affect the classification 
of the road. Thus, an agricultural road may have a 
residential character for a limited distance from the 
city line, then gradually become purely agricultural, 
and then blend into the scenic before it becomes a part 
of another road leading to another town or city. 

In the cases of agricultural roads and residential 
roads most of the travel originates along or in the 
region immediately tributary to the road. In the case 
of scenic roads the major portion of the travel is at- 
tracted to the scenic section through which the road 
passes. The character of the traffic itself must be con- 
sidered in determining the location. 

According to the figures of the United States Office of 
Public Roads and Rural Engineering, the average haul 
of farm products in the United States is nine and four- 
tenths (9.4) miles, and the average cost of hauling from 



ROAD LOCATION 33 

the farm to the market approximately 23 cents per ton 
per mile. As this cost average includes all classes of 
roads, improved and unimproved, it must be consid- 
ered that in sections more remote from the market and 
where the roads are not improved the cost of hauling to 
market is so great that only the most profitable crops 
can be grown and marketed without loss. To this fact 
must be ascribed the abandonment of many farms some 
twenty or thirty years ago in Massachusetts, New York, 
Pennsylvania, and other states. In more recent years, 
since the building of roads has become a fixed policy, 
these lands have all been reclaimed, and now possess a 
high value as farm lands. 

In locating a road through and from an agricultural 
community attention should first be given to the cul- 
tivable area which the road is intended to accommodate 
not only at present, but in the future. In older com- 
munities the selection of a road for improvement as a 
main road is largely a question of choice among existing 
roads, each having its special claims for preferment. 
The facts most necessary to a proper consideration are : 

(1) Accessibility to the greatest cultivable area. 

(2) Expense of securing correction of alignment, 
widening right of way, eliminating sharp corners (in- 
cluding necessary purchases or exchanges of small par- 
cels of land), and avoidance of railroad grade-crossings. 

(3) Cost of construction, including grading, culverts, 

3 



34 PRACTICAL ROAD BUILDING 

bridges, both on the road to be improved and those lead- 
ing to it. 

(4) The maximum grade and the distance to the city 
or shipping point. 

(5) The probability or possibility of the road, after 
improvement, becoming a section of some through route 
between important points. 

The relation of the first cost of construction to the 
various advantages of certain locations is always a deli- 
cate subject. Each individual case must be worked 
out by itself because no two cases are exactly alike. 
Where the location is under the control of state highway 
officials some of the factors are simplified. Where it is 
in charge of county or township officials, who must 
treat and negotiate with officials of adjoining townships 
or counties for the construction of a continuous road, 
much close figuring is required. The local officials 
are usually in close touch with the taxpayers, and tax- 
payers do not always think alike when immediate cost 
is considered with future advantages. 

There is no question, however, that for the agricul- 
tural road the shortening of distance and the lowering 
of grades justifies additional expense. Marketing 
products must be figured on the cost of hauling per ton 
per mile. Slight grades enable larger loads to be hauled, 
and with shorter distance there is established a direct 
and permanent economy. This economy may justify 







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36 PRACTICAL ROAD BUILDING 

under some circumstances the location of diagonal 
main thoroughfares through a large area of section 
line roads. If the distance from a farm to market be 
12 miles, 6 miles north or south, and 6 miles east or 
west, the diagonal distance would be less than 9 miles, 
and the relative reduction in distance would be the 
same at all intermediate points. The cost of marketing 
products would therefore be reduced by more than 25 
per cent, from the region involved. 

Whether the cost of the land for the right of way and 
the cost of construction would justify the establish- 
ment of this permanent economy is a matter for each 
community to determine. The proposition would re- 
solve itself into a form about as follows : 

"Will a 25 per cent, saving in hauling charges justify 
the cost of the new right-of-way which will reduce to 
that extent the hauling distance?" 

From this cost must be deducted the cost of the im- 
provement of the extra length of the longer route; but 
much of this saving will be taken up by building a road 
in a new location, instead of along the line of an old 
road. As a general principle, it may be stated that the 
construction of a main diagonal road through any con- 
siderable farming territory where the roads run at right 
angles, in order to make a short cut to the city or ship- 
ping point, is good policy; for the saving in cost of 
hauling is positive and permanent. The cost of an 



ROAD LOCATION 37 

improvement so located, therefore, should not be 
looked on as an expense, but as an investment, which 
will continue to pay dividends as long as fields grow 
crops. 

The differences in public sentiment in various com- 
munities and the differences in the laws of the several 
states have much to do with establishing roads in new 
locations, and for correcting defects in old locations. 
In some communities a large number of property owners 
will donate the strip of land necessary; then again an 
owner will be found whose avariciousness is such that 
he demands an exorbitant price for his property. In 
some states the condemnation laws are such that a 
great public improvement can be held up for years on 
account of the refusal of a single owner to part with the 
necessary strip of land on terms that his neighbors are 
willing to consider. In most states, however, the land 
may be taken under condemnation proceedings, the 
road built and put to use without reference to the length 
of time the question of compensation is held in the 
courts. 

In a majority of cases the location and improvement 
of a main road through a community so enhances the 
values of the adjacent lands that the owner can well 
afford to donate the right of way. Exceptions occur 
in the case of small holdings, and where improvements 
such as buildings or orchards or other permanent im- 



38 PRACTICAL ROAD BUILDING 

provements must be sacrificed. The local conditions 
are so varied that no specific method may be prescribed. 
The question is one of fairness to all interests involved. 

In residential districts the problem of location is 
more simple. In many cases the district is a suburb of 
a city, and the location of the roads has been fixed by 
the original promoters of the residential colony. Where 
this was done several years ago, the central idea was 
probably accessibility to the railroad station, or to the 
interurban trolley line, which would provide trans- 
portation to the city. Since the popularization of the 
automobile this viewpoint has largely been changed, 
many suburbanites having their autos in which they 
ride regularly to and from their business in the city. 

In this way the location of the main road leading 
from the suburb to the city becomes important. This 
importance is added to by the fact that auto-trucks, 
loaded with fuel and other heavy commodities, and auto 
delivery wagons from the city often take the place of 
the former railroad and local delivery system. Not 
only must the main thoroughfare be direct and of easy 
grade, but the character of many of the streets and side 
roads is changed. This raises the question of the loca- 
tion of roads which must carry the heaviest travel, and 
which for this reason must have the most substantial 
improvement.- 

The location of the residential road must always 



ROAD LOCATION 39 

control the character of the improvement. Where the 
most travel goes should be placed the strongest founda- 
tions and the most enduring surface. It is as wasteful 
to put a cheap and inferior pavement where a first- 
class one is demanded by the traffic, as it is to put a 
high-priced pavement on a back or side street where 
there is little travel. Nearly all of the more expensive 
pavements of today will go to pieces more rapidly under 
a very light traffic than they will under a heavy traffic. 

An instance of this may be noted: The main street 
of a suburban village near one of the medium-sized 
cities was being paved. The street formed a part of 
the main country road leading from a large agricultural 
district to the city. The suburban village authorities 
decided on a high-class expensive pavement, both from 
sentiments of civic pride and economy. 

A gentleman of large means had a palatial residence 
about half a mile back from the road just beyond the 
village limits. His private road branched off the main 
street at about the point where the pavement changed 
to the well-improved but less expensive country road. 

The man, observing the paving of the street while the 
work was in progress, became impressed with its ex- 
cellence, and decided that he would have his half-mile 
of road improved in the same way. He figured that if 
the street in the suburban village would last twenty or 
twenty-five years, under the traffic that it would be 



40 PRACTICAL ROAD BUILDING 

called on to carry, that his road, with its light travel, 
should last almost to the end of time. 

The road was built according to specifications. That 
was twelve years ago. It' was built with a concrete 
base and curbs, brick gutters, and sheet asphalt be- 
tween the gutters. Today the street in the village is in 
first-class condition, carrying a heavy farm and local 
traffic, and with an exceedingly light maintenance cost. 
But the private road has only left of the original con- 
struction the concrete base and curbs. Five or six 
years ago the asphalt and brick were removed and a 
surface given of gravel mixed with some preparation 
which holds it in place, and prevents the formation of 
excessive dust. 

The original surface went to pieces because of lack 
of enough travel to keep it in proper condition. The 
asphalt surface cracked and buckled from the cold and 
heat because there was not travel enough over it to 
keep the surface ironed down. Seeds of grass and weeds 
settled into the filler between the brick, and the growth 
pushed them out of place, let the water under them, and 
the frost did the rest. It was an example of a good 
pavement in the wrong place. 

In locating a scenic road the basis for calculation is 
entirely different. The chief function of a scenic road 
is to attract travel. It may serve the further purpose 
of forming an avenue of transportation for an agricul- 




41 



42 PRACTICAL ROAD BUILDING 

tural section, but in most of the localities where roads 
are built for scenic purposes agricultural production is 
confined to occasional valleys or patches of arable land. 
Sometimes other purposes are served; such as getting 
out timber, moving mine supplies and products, etc.; 
but these various purposes tend rather to detract from 
the importance of the road than to add to it. The 
various industries could probably be better cared for 
by roads so located as to give them more direct routes 
and easier grades, with the scenic element left out. 

The varied character of scenic roads makes impossible 
any set of hard-and-fast rules to be observed in their 
location, or grades, or types of improvement. "The 
Crest of the Blue Ridge" road, extending across the 
Carolinas about the top of that particular range of the 
Appalachian Mountains, requires one kind of treat- 
ment, and the "Columbia River Road" in Oregon re- 
quires another, yet both have the same purpose, that of 
attracting visitors and travelers from other sections of 
country to take advantage of the grand and impressive 
scenery which nature has established, of a favorable 
climate, and of such facilities in the way of places of 
entertainment as may have been provided. 

There is a difference of opinion as to the maximum 
grade which should be permitted on a scenic road. 
Some authorities hold that it should never exceed 5 per 
cent. (5 feet elevation to 100 feet of distance), because 



ROAD LOCATION 43 

that is said to be the steepest grade at which the aver- 
age automobile can operate on high gear. Advocates 
of this theory affirm that the pleasure seeker prefers 
to travel a greater distance rather than shift to a lower 
gear while climbing a steeper grade. Others state that 
the grade, within reason, makes little difference, and 
that an additional charm is given to motoring when 
there are occasional hills to ascend or descend. 

The fact that a location once made is likely to be 
permanent, and that in the course of years the scenic 
road is liable to cause the development of industrial 
resources of the region which will make the road avail- 
able for other purposes, suggests that the grade be kept 
down to the 5 per cent, limit wherever possible without 
too great a sacrifice of view, or extension of distance, or 
the overcoming of other special disadvantages. It fre- 
quently occurs that in maintaining a reasonable grade 
the location must be made along the sides of moun- 
tains, sometimes by a zig-zag course; streams and 
chasms have to be crossed by bridge or trestle, and 
many other unusual conditions encountered. These 
must be studied individually, as no two instances are 
nearly enough alike to come under any general rule 
that may be laid down. 

A qualifying factor in all road location is the question 
of through routes. In some states this is covered by 
state laws, establishing State Highways connecting 



44 PRACTICAL KOAD BUILDING 

important centers. In other states and sections of the 
country Road Associations of greater or less impor- 
tance have a definite influence on local road locations. 
Such organizations as the Quebec and Miami Highway 
Association; the Lincoln Highway Association; the 
Dixie Highway Association; the National Old Trails 
Association, and many others of either national or sec- 
tional importance, have been assiduous in their efforts 
to enthuse local authorities to a point where they will 
locate and improve the particular sections within their 
respective jurisdictions. Much force and impetus 
have been given to the Good Roads Movement by the 
work of these associations, and in the general discussion 
of location of roads the differences between roads of a 
purely local character and those which will accommo- 
date general travel have been clearly brought out. 

It may be assumed that a through route traversing 
a county or other subdivision should be located where 
it will accommodate the greatest number of the local 
population and the greatest amount of local produc- 
tion. Any other basis of calculation would give the 
road more importance as a through route than as a 
local necessity. With the exception of a very few 
roads between very large cities, and a few purely scenic 
highways this is not a fact. While the local usefulness 
of the highway should be the first consideration, care- 
ful attention to the advantages of a constantly growing 




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46 PRACTICAL ROAD BUILDING 

through travel, and to the proper connections at county 
or other divisional lines, will contribute to the highest 
usefulness of the road. 

In locating any new road, or in relocating a road for 
the purpose of securing better grades, or for other 
reasons, modern traffic demands that provision be made 
for a 'line of sight." By this is meant the distance at 
which vehicles approaching each other may be seen 
by the drivers of each. 

A trifling computation shows that two automobiles, 
each running at 20 miles an hour, approach each other 
at the rate of § mile or 3520 feet a minute. Even if 
drivers were always alert, at least half a minute, or 
1760 feet, is the smallest possible amount of time and 
space in which safety can be assured. It becomes 
necessary, therefore, that in locating a road a view of at 
least I mile ahead be provided for, either by sight 
along the road or across the intervening fields. Where 
this is not possible by reason of hillsides or forests, or 
buildings, or other obstructions, cautionary signs of an 
unmistakable character should notify drivers to reduce 
speed. 

In general road locating this provision is not as diffi- 
cult as it may appear at the first glance at the subject. 
Every sober driver knows enough to slow down at a 
sharp turn and keep to the right side of the road; but 
with 2000 feet of road in sight, more or less, the driver 



ROAD LOCATION 47 

is likely to take chances, or to be extra cautious, ac- 
cording to disposition. Every one who has driven a 
motor car will appreciate the distinction. 

To so locate a road that the line of sight will be ex- 
tended to its greatest possible limits is of grave impor- 
tance whether the travel be horse drawn or motor driven, 
or both. In but few states are horse-drawn vehicles 
obliged to carry front and rear lights, which fact adds 
an extra hazard at night, even under the most favor- 
able conditions. Common prudence, however, re- 
quires that a driver be able to see an approaching 
vehicle at a distance which will enable him to take 
reasonable precautions for safety. To accomplish this 
the highway officials under whose jurisdiction the road 
is located must constantly keep in mind the importance 
of the line of sight. 

The great importance of the correct location of a road 
lies in the fact that it is the one element of the road that 
is expected to last for all time. Grades may be de- 
stroyed; surfaces will wear out and require replacement; 
bridges and culverts are subject to damage; but the 
location always remains, either as a monument to the 
intelligence and integrity of those who placed it prop- 
erly, or as a constant and permanent reminder of the 
inefficiency of those who may have been responsible 
for an improper location. 

This is especially true where a road is built with the 



48 PKACTICAL EOAD BUILDING 

proceeds of a bond issue, and particularly in cases of 
long term bonds. The location and the right of way, 
taken together, are the one tangible basic asset which 
does not require maintenance or other expenditure. If 
the location has been wisely made, its value to the com- 
munity increases year by year, in the ratio that the 
prosperity of the people is developed; and when the 
bonds are paid off and cancelled, the people are rich in 
the possession of a road location on which can be placed 
or kept whatever surfacing the needs of a constantly 
changing traffic may require. 

A certain road in the interior of the state of New 
York was located on a line where two land grants 
joined. At one point the road passed over a high hill, 
the distance from the bottom of the hill on one side to 
the bottom on the other being about J mile. The apex 
of the hill was nearly 200 feet above the level of the 
roads on either side, forming grades in some places of 
20 per cent, and upward. 

Over this hill was hauled the marketed products of a 
considerable farming area, perhaps thirty or forty good 
farms, for more than a century. Three or more genera- 
tions of farmers hauled small loads or "doubled up" to 
get their produce over the hill. It was something more 
than one hundred years from the time of the original 
location of that road before the community became 
sufficiently interested to demand a change. 



ROAD LOCATION 49 

It required two or three years of almost constant ar- 
guing by some of the younger men of the neighborhood 
before action could be taken. Then a road was built 
around the base of the hill, practically level, and the old 
hill road abandoned. 

It fell to the lot of one who had been born and reared 
in that neighborhood, but who was making his first 
visit there in more than twenty years, to take a tape 
line and measure the surface lengths of the two roads. 
He found that the new level road around the base of 
the hill was exactly 49 feet longer than the one over the 
hill. 

He pondered. He recalled the struggles of his youth; 
the struggles of his father, and grandfather, and great 
grandfather, and their neighbors in the century work of 
advancement toward prosperity and education and 
higher civilization. He computed roughly the annual 
farm production which had gone over that hill; the time 
wasted; the small loads enforced; the broken hame 
straps and whifHetrees, and a thousand other factors 
brought up bjr memory. 

Then he considered again that 49 feet in a total dis- 
tance of about 1800 feet of hill and level road. Then 
he wrote for a book a chapter on the subject of "Road 
Location." 



CHAPTER III 



ROAD GRADES 



For purposes of discussion the subject of road 
grades must be separated into two phases. One phase 
has reference to a departure of the surface from a level; 
the other deals with the road-bed itself. 

A road is up-grade or down-grade whenever it is not 
level, and the measurement may be made from either 
end of the incline or decline. Beginning at a low point 
and continuing the survey to higher ground, the up- 
grade may be computed in a percentage, which means 
a given rise in each 100 feet of distance. It may be 
stated that while there is no especial reason except, 
perhaps, uniformity of expression, it is an almost uni- 
versal custom to figure grades on the ascending instead 
of the descending scale of measurement. Thus a grade 
of 2 per cent, means a rise of 2 feet in each 100 feet of 
distance. Grades are "light" or "heavy" according to 
the amount of rise per 100 feet figured as a per cent. 

It is a general practice among road builders of ex- 
perience to avoid an absolute level in laying out a road 
for any considerable distance. One of the reasons for 
this is that as there must be a slope to the side ditches 

50 



ROAD GRADES 51 

to enable the water to run off, the ditches would be too 
shallow in the center of the level strip and too deep at 
the ends where the water is to be discharged. It is 
considered better practice, in establishing the grade to 
make the slight inclinations in the road surface so as 
to keep the ditches at a uniform depth. Besides, in a 
region so flat that a nearly level road becomes necessary 
even a slight grade assists in securing a prompt run off 
of surface or storm water. 

In most states where state highways departments 
control, road grades are limited to a maximum of 5 feet 
to the 100, or 5 per cent. Exceptions may be made in 
rare instances for short distances, or a fractional in- 
crease may be permitted where the lay of the land is 
such that a large saving in cost or distance may result. 
These cases are rare, however, when compared with the 
total number of miles of roads improved. Many city 
streets have steeper grades, due to the fact that cities 
were laid out on irregular and hilly surfaces, and im- 
provements made before the necessity for lower grades 
became apparent. 

The principle involved in fixing the limit of steepness 
(the maximum grade which may be allowed on a road) 
is that over which the greatest loads which can reason- 
ably be expected may be hauled at the least expense. 
In studying this problem it is better to use horsepower 
because most motor-driven vehicles are so constructed 



52 PRACTICAL ROAD BUILDING 

that with change of gear they can negotiate almost any- 
ordinary grade. 

The weight of load that a horse can pull on a level 
road or on any grade depends on the surface of the 
particular road. So for general purposes it is better to 
consider the pulling power, or tractive force, of the 
horse as compared with the grade. 

Actual tests have shown that a horse working steadily 
can exert a steady pull of 120 pounds. For a short 
time, as in starting a loaded vehicle or pulling up a 
short hill, this may be increased up to a possible 500 
pounds. Suppose the road surface is one on which a 
pulling power of 120 pounds will haul 1200 pounds of 
load on a level, it has been found that only half this 
load, or 600 pounds, can be hauled up a 6 per cent, grade, 
and only one-fourth, or 300 pounds, up a 10 per cent, 
grade, with the same horsepower. The exception of 
the short distance, or the short space of time in which 
the horse can exert greater pulling power, should only 
be given application when it is absolutely necessary to 
do so. 

A factor which enters largely into the determination 
of the maximum grade is the direction in which the 
heavy loads travel. If it be an agricultural road, and 
the city or shipping point is in the valley with the farms 
accommodated by the road located on the adjacent hills, 
it is reasonable to suppose that the greater part of the 



ROAD GRADES 53 

heavy traffic over the road will be down grade. In such 
cases a steeper grade is permissible than in localities 
where the railroad and shipping points are high up on 
the side of the hill, with the farms in the valley. In 
the latter case the heavy loads must be hauled up hill, 
and grades should be made as easy as the topography 
and the elevation will permit. Care must be taken 
when the heavy traffic is down grade not to have the 
grade steep enough so that brakes on wheels will cause 
injury to the road surface. 

Authorities differ greatly as to the steepness of the 
grade on which various surfaces may be used. An earth 
road has been accustomed to be considered as available 
at any grade which was possible of ascent or descent. 
In certain hilly regions very steep hills are traversed. 
Grades up to 20 or even 25 feet to the 100 are employed 
and kept in fair condition. When a country road be- 
comes too steep for any hard surfacing, the only alter- 
native within the limits of reasonable cost is to leave 
it with a surface of earth or gravel which will not wash 
badly. On steep city streets a pavement of stone 
blocks or cobble-stones is usually used. A cobble- 
stone pavement is reported on a street in San Francisco 
which has a grade of 51 per cent. — 51 feet rise in 100 
feet of distance. 

Macadam and gravel roads have been used on almost 
any grade. There are numerous examples of their em- 



54 PRACTICAL ROAD BUILDING 

ploy men t on grades up to 18 or 20 per cent. Asphaltic 
macadam may be used up to a grade of 7 or 8 per cent. ; 
asphaltic concrete, up to a grade of 5 or 6 per cent. ; vitri- 
fied brick, up to a grade of 6 or 7 per cent.; concrete, 
up to a grade of 4 or 5 per cent. Special forms of brick 
and special corrugations in concrete, both made for 
hillside use, may add to the steepness of the grade where 
they may be permitted. 

These figures are relative rather than arbitrary. 
They may be modified by any one of a variety of local 
conditions, and especially by the character of the traffic. 
Wide and narrow steel tires, pneumatic and solid rubber 
tires, the weight of the heavy loads, and other factors 
must be considered when determining the maximum 
grade of a road on which a certain surfacing is to be 
placed; or determining the proper surface for a road of 
a given grade. 

Further modification of the figures may depend on 
the details of construction. If the surface be made 
somewhat rough, or so that it will wear rough, by plac- 
ing reasonably large sized stones in the top course a 
better foothold will be given than when the surface is of 
fine stone or fine gravel. With the better foothold a 
slightly steeper grade is permissible. In the deter- 
mination of grades, however, the primary thought must 
always be to keep the percentage as low as possible. 

In establishing road grades consideration must be 



ROAD GRADES 



55 



given to the level of intersecting roads; to the level at 
which bridges and culverts must be constructed, and 
to the general scope of the road itself. When a road 
is being built for a distance involving several miles 
with an ascending grade, good practice does not per- 
mit, except under extraordinary circumstances, a down 




Fig. 4. — A long side-hill grade in Ohio. 

grade at any point in the road. An instance of this 
was presented at a road convention not long ago, when 
it was stated that in building a road from sea level to 
the crest of the Blue Ridge Mountains, a rise of some 
5000 feet, no steeper grade than 4 feet 6 inches to the 
100 feet had been employed, and no down grade what- 
ever permitted along the ascending route. Of course 



56 PRACTICAL ROAD BUILDING 

this does not apply to bridge approaches nor to condi- 
tions made necessary by railroad crossings, road cross- 
ings, or other purely local factors. As the general 
trend of the road was toward a higher elevation, the 
grade of its different sections must conform to the 
general plan. 

In establishing road grades special treatment of curves 
is necessary. When a curve is approached there should 
be a gradual reduction of the grade so that when the 
curve is reached the grade should not be more than 
half as steep as on the straight road. For instance, 
if the grade of the straight road is 4 feet to the 100 feet, 
on the curve it should not be more than 2 feet to the 
100 feet of distance. This rule applies to any ordinary 
curve. If the curve be a short one the grade should be 
reduced still more, and on very short curves should be 
reduced to a level. 

By a "short curve" in this connection is meant the 
degree of curvature, or the radius of the curve; not the 
length of the road on the curve. A curve is a part of a 
circle, like a part of the rim of a wheel. The radius 
of any curve is the distance from the rim to the center 
of the circle, as to the center of the axle on which the 
wheel revolves. Thus a radius of 100 feet would mean 
that the curve would be a short section of a circle 200 
feet in diameter. The measurement is usually made to 
the center line of the road, and the road should always 



ROAD GRADES 



57 



be widened on a curve. The 
best authorities seem to con- 
sider that the widening should 
be on the inside of the curve, 
keeping the outside to a true 
curved line parallel with the 
center line of the road. 

On the national roads of 
France the radii of curves are 
established at a practical min- 
imum of 165 feet, while on com- 
munal or country roads curves 
as short as 50 feet radii are per- 
mitted. In the measurement of 
curves all engineers do not seem 
to follow the same practice, 
some measuring from the inside 
line of the road, others from the 
center line, and still others from 
the outside line. This can be best 
illustrated by the turn of a street 
where the curb comes to a corner. 
If the inside measurement were 
taken, the radius would be zero, 
as the same point would be the 
beginning of one straight section 
and the end of arfbther. If the 



O 



c3 

Sh 

bfi 
-£ 
bfi 



T3 



T3 

o 

^3 



fab 



58 PRACTICAL ROAD BUILDING 

measurement were made on the center line, and the 
street were 40 feet wide, the radius would be 20 feet; 
and if the outside line were taken as a basis for measure- 
ment, the radius would be 40 feet, the full width of the 
roadway. On country roads, however, sharp turns 
rarely become necessary, the usual right of way being 
wide enough to make a reasonable curve. 

Figures by engineers show that on a 12-foot road the 
radius of a curve must be at least 100 feet to accommo- 
date a four-horse team and long vehicle with a total 
length of 50 feet. If the road is 18 feet wide the radius 
of the curve can be reduced to about 66 feet and still 
keep the rear wheels on the roadway. On most roads, 
however, it is not the extra long teams and vehicles 
which must be provided for, but the facility and safety 
with which shorter ones may pass each other. 

In the construction of the road-bed to which the term 
"grade" is usually applied, several factors must be 
considered. If the grade is to be built up, as an em- 
bankment on low ground, or if it be necessary to make 
a cut through a hill, the character of the soil and the 
amount of earth to be moved are the important feat- 
ures. Where a hill and a hollow come together the 
matter is simplified, as the earth taken from the hill 
can be dumped into the hollow with the least possible 
expense. When there is a haul of any considerable 
distance, either to dispose of earth taken from a cut or 



ROAD GRADES 59 

to bring earth for a fill, the expense grows rapidly in 
proportion. 

By studying the cost accounts of a large number of 
contractors it has been found that in moving earth 
from a cut to a fill drag scrapers can be used to the best 
advantage when the distance does not exceed 100 yards; 
after that wheeled scrapers are best up to a distance of 
300 to 400 yards. For longer distances dump wagons 
are more economical. 

In making the fill the earth should be deposited in 
layers of approximately 8 to 12 inches in depth. Each 
layer should begin next to the hillside and be built 
outward as far as the earth from the adjacent cut is 
intended to be used. The first deposits of earth should 
be along the center-line stakes of the road, and a slight 
slope from the center to the sides should be maintained. 
The bottom or base of the fill must be made to its full 
width to secure the best results. The some-time prac- 
tice of building up the center and dumping earth over 
the sides of the fill to complete it to the proper width 
has not been found satisfactory. 

Where it is intended to complete the road during the 
same season a heavy road roller is necessary to pack the 
earth as each layer is placed. An important fact to be 
considered in this connection is, that while loose earth 
at first occupies a greater space than it did in its original 
position, when compacted, either under heavy rolling 



60 PRACTICAL ROAD BUILDING 

or by settling when time be given, it will occupy much 
less space than it did in its former bed. For instance, 
100 cubic yards of measured earth taken from a cut, 
placed in an embankment, and so compacted as to make 
a proper fill for a road, will shrink to about the follow- 
ing figures: 

One hundred cubic yards of gravel or sand will com- 
pact to about 92 cubic yards; of clay, to about 90 cubic 
yards; of loam, to about 88 cubic yards; and of loose 
surface soil, to about 85 cubic yards. Clay if subjected 
to the action of water will have a much larger shrinkage. 
These figures should always be taken into consideration 
in providing the earth necessary to make a given fill or 
embankment. They apply alike whether the earth is 
compacted by heavy rolling, or whether it is left over 
for a season to settle before completing the road, which 
is a custom in some sections of country. 

The side slopes on fills and cuts must be at such an 
angle as to insure stability, and at the same time not 
waste material or labor. When the same earth is used, 
the slope on the sides of the fill may be figured the same 
as the side slopes of the cut from which the earth was 
taken. The tendency of the earth to wash into small 
gullies or to wash or settle away under storm or frost 
conditions must be considered. 

In general, the slope is figured by the foot on the level 
compared with a foot of elevation. The usual practice 



ROAD GRADES 61 

is 1 J to 1, which means 1| feet on the level to every foot 
in height, in most classes of earth. This is usually em- 
ployed with sand and gravel. Some kinds of earth will 
stand a slope of 1 to 1 when it is firmly packed. Some 
kinds of clay will not stand unless the slope be 4 or 5 
feet on the level to 1 foot in height. 

The earth should be spread over the entire width 
required at the beginning of the work of making the 
fill. Take a 24-foot roadway as an instance, to be 
placed on a fill 10 feet high. If the slope is to be 1| to 1 
the bottom course of earth should be 54 feet wide, al- 
lowing the 24 feet for the roadway and 15 feet for the 
slope on each side. By depositing the earth in this 
manner, keeping the fill a trifle higher at the center than 
at the sides, rolling close to the edges, and making each 
successive layer of earth narrower, the best results are 
obtained. 

In every instance the factor of common sense (horse 
sense) on the part of the contractor or official in charge 
of the work must be reckoned with. An instance in 
point may be mentioned: 

It had been decided to widen an existing road from 
24 to 40 feet. In one place the road was built on a fill 
for a distance of about 300 feet, the fill being about 30 
feet high over the lowest part of the gully, and tapering 
gradually to the road level at each end. In widening 
the fill and to provide special stability a new fill, 20 



62 PRACTICAL ROAD BUILDING 

feet in width,, was built along and against one side of the 
old one. The culvert was lengthened, the earth placed 
in position, and compacted with a heavy roller. 

The old embankment had been in place for several 
years, and the slope had accumulated a heavy sod, 
and had become covered with a dense growth of 
rank weeds. Common sense should have taught the 
official in charge the necessity of taking a side hill plough 
and cutting off that sod, and removing or burning the 
weeds, so that the fresh earth should be made to amal- 
gamate as closely as possible with the compacted earth 
of the old fill. This was not done, however. The fresh 
earth was deposited on top of the sod and weeds, rolled 
as solid as possible, and the road surface put on. 

The next summer a lengthwise crack appeared in the 
surface of the road about where the junction of the new 
and old fills was located, and that portion over the new 
fill settled slightly. The officials were still discussing 
what steps to take to protect the road when the fall 
rains came, and it was decided to let the matter go over 
until another season in the hope that the difficulty 
would adjust itself. The second summer there was an 
opening in the surface averaging a foot in width and the 
surface over the new fill had settled 4 to 6 inches, re- 
quiring practical reconstruction. 

Investigation showed that the sod and other vege- 
tation in the course of decay had formed a thin parti- 



ROAD GRADES 63 

tion line between the old fill and the new; and that par- 
tition was of such a character that the new or outer fill 
had been caused to slide downward and outward to an 
extent which had practically ruined the surface. The 
difficulty was overcome at considerable expense and no 
one connected with that job is likely to commit the same 
error again. 

In building a road grade across a low marshy section 
of ground it is wise to make a careful investigation of the 
subsoil and of the earth strata underneath. It some- 
times occurs that underneath the marsh is a thin stra- 
tum of clay perhaps only a few inches thick in places, 
and underneath the clay a layer of either very soft mud 
or quicksand. If the fill is to be a heavy one, so as to 
bring the road grade well above the adjacent marsh, it 
is very likely to break through the layer of clay, and 
form what for want of a better name is termed a "sink 
hole." Road builders in many sections of the country 
have encountered these conditions, and have spent large 
amounts of money putting on additional earth, which 
would soon settle again, making more earth necessary. 

While each individual case must be treated accord- 
ing to the conditions found to exist, a number of con- 
tractors have reported that in their experience it is 
safest and most economical to find out the depth of the 
clay or hard earth or even soft rock underlying the low 
ground by cutting holes in it at regular intervals along 



64 PRACTICAL ROAD BUILDING 

one side of the road location; then determine the char- 
acter of the earth beneath within iron rod. If it be of 
a character that would develop into a "sink hole," it 
has been found cheapest in the long run to drive a row 
of piles close together on each side of the base line of the 
proposed grade embankment. The particular spots 
where this is found necessary are not usually very large 
in extent; and if the piles are driven down to the hard 
earth underneath a complete protection of the fill is 
established, and the settlement is likely to be very slight 
In locations where the grade is built in a cut there is 
a variety of conditions. Sand or gravel; earth, with or 
without being mixed with stone; hard-pan; rock, soft 
or hard; boulders, from sizes which can be easily 
handled to those which must be blasted to pieces; clay, 
ranging from that which will dissolve easily in water to 
that on which water has but little effect — these are 
all subject to different treatment. In some cases the 
plough and scraper, as previously stated, will be found 
economical. If the cut be fairly deep, a steam shovel 
may be used; and on jobs where there is a large quantity 
of earth to be moved the portable railway and dump 
cars are employed. Where rock or heavy boulders are 
encountered a derrick of some sort is a money saving 
part of the equipment. Even a portable hand derrick, 
operated by a windlass and cranks, will often effect a 
saving in the cost of loading rock for removal. Gener- 



ROAD GRADES 65 

ally the equipment should be consistent with the work, 
so that no part of it should be idle and creating expense 
while other parts are in use. 

It has occurred frequently that there were more 
ploughs to loosen the earth than scrapers or wagons to 
take it away; or that there were more moving facilities 
than there was earth ready to move. Steam shovels 
with expert and high-priced operators are often idle 
part of the time because of a scarcity of wagons or 
dump cars. On the other hand, it sometimes occurs 
that there are too many wagons. Where drill work is 
going on for the blasting of rock, the drills can proceed 
without loss of time by going ahead into new work, 
but the arrangements for removal must be carefully 
proportioned to avoid useless expense. 

What is known as a " vertical curve" is employed in 
changing from one grade to another. If a section of 
road has a grade of 2 feet to the 100 feet a point may be 
reached, as at the foot of a hill, where the grade will be 
increased to 5 feet to the 100 feet. In making the 
change, so that it will not be abrupt from one grade to 
another, it should be made gradually; and at the top of a 
hill the up-grade should be reduced gradually to a level, 
and the down-grade on the other side approached 
gradually. Where property damages are involved, it 
may be well to have these ■ 'vertical curves" scientific- 
ally determined. For all ordinary purposes good com- 

5 



66 PRACTICAL ROAD BUILDING 

mon sense may be depended on to make a change from 
one grade to another without abruptness. 

In building up a grade by a fill or embankment, any 
rock or large stones should be used at the bottom, with 
earth above. No large stones should lie near the sur- 
face. The reason for this is that earth never packs 
so hard but that it will settle to some extent; and large 
stones, forming a rigid substance, will, if near the sur- 
face, make the surface irregular, and distort the sur- 
facing material in the spots where they occur. 

The principles involved in establishing and con- 
structing a road grade relate principally to keeping the 
road from being level or flat, and from having a grade 
of more than 5 per cent. ; constructing the grade so that 
the proper gradient will be maintained in cuts or on 
fills, or on a level where a level is necessary, and com- 
bining the level with the grade without abruptness. 
Then the building of the grade, either by embankment 
or cut, so as to maintain the roadway in proper condi- 
tion to carry the surface that is to be placed upon it. 

Given the location of the road, the center line of the 
road is easily established. This should be perfectly 
straight as far as the road extends in one direction. 
Whether the gradient be ascending or descending, the 
center line stakes should continue in a straight line until 
a curve is reached. The side ditches, the fills, the cuts 
must be measured at the proper distance from the center 



ROAD GRADES 67 

line. The slopes of the fills and the outer slopes in the 
cuts must all be measured from the center line of the 
road. 

In making contracts for building road grades it 
sometimes occurs that one contract ends at about the 
edge of a hill through which a cut is to be made. The 
adjoining contract may be over low ground where a 
fill is necessary. In such case each contractor would 
naturally make his bid on the amount of earth to be 
removed or to be supplied. Unless it be by pre-ar- 
rangement, where the two contractors may work to- 
gether with a proper reduction of cost, the community 
will find itself paying two prices : one for the removal of 
the earth from the excavation or cut, and the other 
for the cost of earth to be put into the low ground to 
make the fill. By having the cut and fill under one 
contract, and as nearly as possible covering the same 
amount of earth excavated from one point and filled in 
at another, with a single cost for the movement of the 
earth, much money may be saved. 



CHAPTER IV 



ROAD DRAINAGE 



Drainage is considered by most road builders the 
most important factor in the construction of any road. 
Water may be considered the most destructive agent 
which can be encountered in building any road and in 
keeping any road in condition. Provisions for taking 
the water off the road surface and from underneath the 
road, and getting it entirely away from the roadway, 
must be comprehensive and complete if the road is to 
remain in good condition. 

There are two distinct phases of the road drainage 
problem: One is the taking care of the surface water, 
storm water, melting snow, etc., getting it quickly into 
the side ditches and carried away through proper 
drainage channels. The other relates to the subdrain- 
age; getting the water out of damp or wet soils or sub- 
soils, so that the foundations of the road may be pro- 
tected. In the final discharge the waters from above 
and below are usually carried off through the same 
channels, though it sometimes occurs that each may 
have an independent outlet. 

Surface drainage begins with the slope or crown of the 
road surface. The height of the crown and its slope 

68 



ROAD DRAINAGE 69 

differs with each type of surface, and are specially 
mentioned in the various chapters devoted to road sur- 
faces. In practically all country roads which are given 
hard surfaces there are shoulders or "berms," as they 
are sometimes called, extending from the hard surfaced 
portion to the side ditch. As a general rule these 
shoulders maintain the same slope as the hard surface, 
unless there be some reason for changing it. 

In building any hard surface road the shoulder 
should be provided for either by excavating into the 
solid earth for the roadway, leaving the shoulder stand- 
ing, or by building up a shoulder with good, firm earth, 
and rolling it to a solid condition. When the road is 
built care must be taken that the road material and 
the shoulder are packed firmly together; otherwise 
water will seep into the joint and cause damage either 
to the roadway or to the shoulder, or to both. 

The shoulder should never be higher, not even by the 
fraction of an inch, than the hard surface of the road. 
If sod is permitted to form on the shoulder, care must 
be taken that it is kept down so that it will not impede 
the free flow of water from the road surface to the side 
ditch. In some soils, where the water has a tendency 
to soak into the earth, it is well to encourage the forma- 
tion of sod. In a specially sandy region, where the 
sand is of a quality that when dry it is likely to be car- 
ried away by the wind, special kinds of sod-forming 



70 PRACTICAL ROAD BUILDING 

grasses are encouraged for the protection of the shoulder 
itself. But if the soil is such that the water will run 
off readily, it is better that the sod be not permitted to 
form or other vegetation to grow. 

Over the shoulders the water gets to the side ditches 
of the road. Or, if the road be on an embankment or 
fill, the water spreads to the adjacent fields and finds 
its way into the natural channels of the drainage of the 
region. It can be readily seen that if the level of the 
road is materially higher than the surrounding country 
there is no need for side ditches except perhaps at the 
bottom of the embankment, to direct the water to the 
proper outlet. If the road is in a cut it must have a 
side ditch on each side, the same as if it closely approxi- 
mates the general ground level. If it is on a side hill 
it must have a side ditch on the side next the hill, the 
water from the outer side draining away naturally. 

In the past there have been three kinds of ditches 
which seemed to have popular approval: the wide flat 
ditch, the V-shaped ditch, and the ditch with nearly 
vertical sides and flat bottom. Each has been used 
whenever, in the judgment of the officials, the nature of 
the soil would permit their use. Modern practice, 
however, favors the broad flat ditch for a number of 
reasons. It will carry more water without developing 
a swift current; it is not subject to so much wearing 
away by the current nor to obstruction by cave-ins 



ROAD DRAINAGE 



71 




of the earth at the sides; and whatever moisture is left 
dries up more quickly because of 
the greater area of exposure to 
the air and sun. Besides these 
reasons which apply to the drain- 
age duty of the ditches, there is 
the safety of traffic on the road 
to be considered. If the ditch be 
wide and flat the road shoulder is 
usually graded gradually down to 
the bottom of the ditch, so that a 
vehicle running into the ditch is 
not in danger of capsizing or other 
damage; while with deep narrow 
ditches a vehicle going at any con- 
siderable rate of speed which in- 
advertently gets a wheel into the 
ditch, either in darkness or by de- 
fective steering or apparatus, or 
through plain carelessness, meets 
with disaster. Not infrequently 
have lives been lost by reason of 
narrow deep ditches, which might 
otherwise have beensaved. 

When the road is built on a side 
hill, or where there is any consider- 
able area from outside the right of 



— * 3 




I 



CO 

S 



72 



PRACTICAL ROAD BUILDING 



way which drains toward the road, back-ditching often 
becomes necessary. This consists of cutting a ditch 
parallel with the road a short distance up the hill, which 
will receive the surface water from the area above and 



*&P 




'"" UM " ,w 'J'% i a=v s> 



To V 



Crass sec / '/os? of em^aoAmerff 



Fig. 7. — Roadway drains itself. 



"«^ •••it 



carry it to the point of delivery. This back-ditch keeps 
the heavy volume of storm water from flooding the 
side ditch of the road, and also prevents the wash of 
sediment into the road ditch. 




Fig. 8. — Culvert under a side-hill road to carry the water from 
the ditch on the upper side. 

There is much difference of opinion as to the minimum 
and maximum grades at which a side ditch may be 
constructed. Some road builders assert that a grade 
of 2 inches per 100 feet is the least grade that should 



ROAD DRAINAGE 73 

be employed. Others maintain that a properly con- 
structed ditch having a fall of \ inch to the 100 feet will 
carry off the water under all ordinary circumstances. 
So slight a fall, however, is not likely to create a current 
that will permit the ditch to keep clear of sediment. 
This is quite an important feature in localities where 
litter, in the form of dead leaves or other vegetation, 
is likely to be blown by the wind into the ditch. Un- 
less the grade of the ditch is steep enough so that the 

K „ 

^> ''III, ^wmwintiiiiuinn 

c^-^ww^ tg ^y^il>Ory sto»* or 

jroofBofce/nenr 
Cr&&s Secf/arn -f/7rot/fA ctyf. acrfer w/tere 

/recessary /» 
prevent usasn- 

Fig. 9. — Water must be carried to the end of the cut. 

water will carry off accumulations then it will be neces- 
sary to have the ditch cleaned out at frequent intervals 
of time. 

Water should not be carried too great a distance in 
side ditches before being given an outlet which will take 
it off the right of way. The distance that it may be 
carried, however, depends on so many conditions that 
much must be left to the judgment and common sense 
of the road builder. If the grade be nearly level, not 



74 PRACTICAL ROAD BUILDING 

more than 2 to 4 inches to the 100 feet, the water can be 
carried several hundred feet without damage if provis- 
ions are made for taking care of the volume of water 
which may come from heavy rains. Such provisions, 
when the water cannot be taken away within a shorter 
distance, usually consist of making the ditch wider and 
deeper toward its lower end. 

Take a sudden rainfall where an inch of water may 
fall within a couple of hours, with a road 30 feet wide 
between the centers of ditches, 15 feet from the center 
of each ditch, there will be 15 inch-feet, or 1 \ cubic feet 
of water to be carried off for every foot in length of 
road. One hundred feet of road would shed into each 
side ditch 125 cubic feet of water. At 200 feet this 
would be increased to 250 cubic feet, and so on in pro- 
portion, until an ordinary side ditch would be taxed to or 
beyond its capacity. 

If the road and ditch be on a heavy grade the prop- 
osition requires no less study and judgment. With a 
swift current and a constantly increasing volume the 
water is likely to wash out either the bottom of the ditch 
into a deep gulley or wash out the side of the road, or 
both. This is particularly true if the earth is soft or 
sandy; most alluvial soils are easily washed, and in all 
such soils care must be taken that the water does not 
obtain either too great a volume or velocity. Where the 
earth at the bottom of the ditch is of hard-pan, or hard 



ROAD DRAINAGE 75 

gravel, or some kinds of hard clay or hard loam, it 
will stand a good deal of rapidly flowing water without 
much damage. It must be the duty of the road builder 
when constructing the ditches to thoroughly inform 
himself as to the character of the earth in which he is 
working, and make his plans accordingly. 

Where there is a heavy grade there is almost inva- 
riably some means of getting the water away from the 
road at frequent intervals, at most every few hundred 
feet, and turning it into some natural water-course or 
low place where it can be turned into natural drainage 
channels. No water should ever be carried in a road 
side ditch further than to a point where it is possible 
to dispose of it off the right of way, except where dam- 
age to private property is involved. When such a 
drainage-point is reached the water must be taken 
through a culvert or pipe from the upper to the lower 
side of the road and turned into the drainage channel. 
The culverts must be of sufficient size to carry all pos- 
sible volumes of water to which they may be sub- 
ject, and placed at such a pitch that they will not only 
carry off the water, but will keep themselves washed 
clean of sediment. 

When water is turned over the side of a bank from 
the outlet of a culvert or ditch, it may be necessary 
to protect the bank so that it will not wash out. This 
may be done by making a trough of planks, or by build- 



76 PRACTICAL ROAD BUILDING 

ing a stone wall with the stones sloped outward and 
downward — on the same plan that shingles are placed — 
or, what is far better if the means permit, building a 
concrete or masonry channel from the end of the culvert 
or ditch to the waterway below. The fact must be 
kept in mind that even a small amount of water, run- 
ning down a steep bank, without protection to the 
bank, will wash it away gradually; and when a flood of 
water comes the wash is likely to be great enough to 
undermine a considerable portion of the road if the 
bank is not properly protected. 

When the water is carried through a culvert or pipe 
from one side of the road to the other the culvert or 
pipe should not be squarely across the road, but at an 
angle which will carry the water in a down-hill direc- 
tion. The opening to the culvert from the inside road 
ditch, if on the same or an increased down grade, should 
be curved, so as to avoid a direct heading for the 
water. If, as frequently happens, the culvert may be 
placed at a lower level, so as to extend underneath the 
embankment, so as to discharge the water near the bot- 
tom of the bank on the outside, it may be necessary to 
construct what is known as a "drop inlet." This drop 
inlet may be made in a variety of ways and from various 
materials, depending somewhat on the depth. Con- 
crete or stone laid in cement mortar are usually con- 
sidered the most durable, and therefore the most 



ROAD DRAINAGE 77 

economical in the long run. The drop inlet should 
extend a few inches below the bottom of the culvert 
opening for the double purpose of catching matter 
which might clog the culvert, and for furnishing a 
"water cushion" for the falling water. The size of the 
drop inlet must be gauged like the ditch and the culvert 
so that it will carry any reasonable amount of water 
which may reach it. It should be protected at the top 
by a grating. 

Occasionally instances are found where for several 
hundred feet on a fairly steep grade there is no practical 
way of getting the water away from the road without 
heavy expense. In such instances some excellent road 
builders have laid sewer pipe underneath one of the 
side ditches, with openings into it every 200 or 300 
feet. The water from the other side of the road is 
carried across in culverts at similar intervals and turned 
into the pipe which carries it to the bottom of the hill 
or to the waterway. In this way the side ditches are 
relieved of the volume of water before it becomes great 
enough to do much damage. 

There are few sections of country which do not fur- 
nish a natural outlet for drainage; and in nearly every 
section there can be found records of rainfall and drain- 
age areas of given streams. These data should be con- 
sulted in determining the size of ditches and culvert 
openings. Often the most accurate figures are those 



78 PRACTICAL ROAD BUILDING 

found in the offices of the engineering departments of 
railroads, and reliable topographical surveys have in 
many cases been made by state or federal authorities. 

In every instance the purpose of the surface drain- 
age of a road must be kept in mind. The slope of the 
road from the center to the side ditches; the grade of 
both the road and ditch; the entrance to the culvert, 
the culvert and the discharge therefrom; the protec- 
tion of the bank; the use of sewer-pipe under the 
ditch; the connection with a natural waterway — all 
must be parts of the plan to take away the surface 
water from the road, with the least expense and with 
the greatest permanency of construction. 

Subsurface drainage, while equally important to the 
life of a road, has in many cases been given less atten- 
tion than it deserves. Some otherwise good road 
builders have overlooked the fact that it is as neces- 
sary to get water from under the road as it is to get 
it off the surface. 

Climatic conditions and the nature of the soil are the 
most important factors in subdrainage. When a road 
is built on an embankment of sand or gravel, or of soil 
in which sand or gravel predominate, there is no need 
for subdrainage. Under these conditions the earth 
drains itself. The same is true if the road is on fairly 
high ground with a similar soil. But most soils other 
than these retain water in their composition unless 



ROAD DRAINAGE 79 

there is a direct means of draining it off into regular 
drainage channels. Soils which consist largely of clay 
or other plastic material are liable, unless properly 
subdrained, to become practically impassable in wet 
weather, and nearly every soil except self-draining 
sand and gravel is likely to heave with the frost and 
become honeycombed when the thaw comes. It is to 
rectify these conditions that subdrainage becomes 
necessary. 

In low places ponds of water along the roadside, if 
permitted, are likely to keep the subgrade saturated. 
Of course, this water should be carried off by the sur- 
face drainage provisions, but this does not always seem 
to be possible. In such cases subdrainage must be put 
in for the protection of the road. Sometimes springs 
from hillsides or from ground higher than the road will 
keep the earth under the roadway saturated for a con- 
siderable distance. Sub drains are necessary to take 
the water away. There may be a stratum of rock under 
the roadway through which water may seep or the rock 
may be so shaped as to hold water, which will be very 
damaging to the road if not removed. 

Some kinds of loams hold water almost as readily as 
clay; and the clearest guide as to what soils sub- 
drainage is needed in is to observe the amount of ex- 
pansion when the ground freezes in winter. The ex- 
panding of the earth loosens the particles from each 



80 PRACTICAL ROAD BUILDING 

other; then when the thawing process takes place — 
and the ground thaws from the bottom as well as the 
top — the soil, softened by the water, is churned up by 
the travel, and it takes days and sometimes weeks for 
the road to dry out. When it does dry out it is usually 
badly rutted because of the fact that the drying began 
at the top, and in its earlier stages wheels would break 
through to the softer mud below. If the road has been 
improved with a hard surface, then the heave caused 
by the frost and the settlement caused by the thaw are 
likely to leave the surface cracked and broken and sub- 
ject to early disintegration. 

Many road builders consider that the best and cheap- 
est method of subdrainage is by means of ordinary farm 
tile or pipe, made either of vitrified clay or of Portland 
cement concrete. The concrete pipe may be made on 
the ground if the materials are convenient. This course 
is followed by some quite prominent road officials and 
by many contractors. 

The molds for concrete pipe are comparatively in- 
expensive, and the work of making them can be carried 
on under a shed or other shelter during rainy weather, 
or at other times of enforced idleness on the road con- 
struction work. Only the best Portland cement should 
be used and mixed with fine sand and gravel in the pro- 
portions of 1 part cement, 2 parts sand, and 3 parts 
gravel. Some authorities claim that there should be 



ROAD DRAINAGE 81 

but 4 parts of sand and gravel combined, which pro- 
portion will certainly add to the strength of the pipe. 
The gravel must be clean and free from any possible 
coating of clay or other surface covering. It is better if 
the gravel be washed, and no individual pebble should 
exceed in diameter one-half the thickness of the wall of 
the pipe. Gravel which will pass through a f-inch 
mesh sieve is usually considered as large as it is advis- 
able to use under any circumstances. 

The concrete should be mixed wet enough so that the 
water will be forced out of the top of the mold and 
should be rammed into the mold until the water no 
longer appears at the top. The ramming, however, 
should be done quickly, so as to be completed before 
the concrete begins to set. Concrete pipe should season 
for at least two or three months before being used, and 
the temperature should not be allowed to get within 
less than 8 or 10 degrees above the freezing-point. 

To determine what size of pipe to use requires the 
exercise of good common sense. There are but few 
data on the subject, by reason of the fact that after the 
pipe has been placed undergound there is no practical 
means of measuring the flow of water through it, or how 
much more or less would have flowed through a larger 
or smaller pipe. The nearest suggestion that can be 
given as a practical guide is the experience of farmers 
in the neighborhood where the road is to be subdrained, 
6 



82 . PRACTICAL ROAD BUILDING 

who have used pipe or tile in the same kind of soil and 
know whether the size they used was large enough to 
serve the purpose. The usual custom is 4 to 6 inches 
in road work. 

All clay pipe should be thoroughly vitrified, but it is 
not essential that it be glazed. The sections are usually 
made 1 foot long for the smaller sizes and 2 feet for the 
larger sizes and with bell and spigot ends. Concrete 
pipe is made with square ends and of practically the 
same lengths, as compared with the size, as the vitrified 
clay pipe. The joints of the concrete pipe are usually 
wrapped in tar paper to keep the sediment from finding 
its way into the pipe, and also for maintaining a correct 
alignment of the pipe during the filling in process. 

There are various other kinds of drains which are 
often used. One is a loose stone drain. In construct- 
ing this drain the trench is dug to the proper depth and 
grade, and about a foot wide at the bottom. Broken 
stone or gravel of coarse sizes, ranging from 1J to 3 
inches, is put in the bottom of the trench to a depth of 
about a foot; then a layer of smaller stone or gravel to 
prevent the earth filling from working down among the 
larger stones, and then the trench is filled. Another 
type of drain may be built of flat field stone by putting 
a layer along the bottom, then a row of stones along 
each side, and another layer of flat stones for the top. 
Sometimes small logs are used laid a few inches apart 



ROAD DRAINAGE 83 

in the bottom of the trench and covered with flat 
stones. 

None of these drains, however, seem to give the satis- 
factory results which are found by using pipe. They 
are much more likely to clog up and require expensive 
overhauling. Besides, there are liable to be differences 
in the character of the soils which would make such a 
ditch while perfectly good in one place, a source of 
danger from undermining or washing in another. 

There are several ways of laying the subdrains, es- 
pecially if they be of pipe. Probably the practice most 
generally employed is to place them underneath the 
side ditches, at a depth of about 3 feet below the bottom 
of the ditch. This depth is not arbitrary; it may be 
necessary to place it deeper in some soils and not quite 
so deep in others. Sometimes a single line of pipe is 
placed under the center of the roadway; but this method 
is not recommended except in rare instances, for the 
reason that any damage to the subdrain would damage 
the road and repairs could not be made without digging 
up the road surface. On heavy grades the subdrains 
should be laid under the shoulders of the road to avoid 
digging up the earth at the bottom of the side ditches, 
and so loosening it that it would wash out with a heavy 
rush of storm water. 

Sometimes the subdrains are made so as to lead from 
the center of the road each way, extending diagonally 



84 PRACTICAL ROAD BUILDING 

down the grade and emptying into the side ditches. 
These transverse drains are also necessary in places 
where there is a springy or spongy spot of earth under 
the roadway. 

The trench for a 5-inch pipe is usually made 12 inches 
wide at the bottom with sides slanting a trifle outward. 
In some cases a special tool is used to shape the center 
of the bottom of the ditch to fit the pipe. In other 
cases a layer of coarse sand or fine gravel is placed in the 
bottom of the trench in which the pipe may be bedded. 
Sometimes, but not often, a board is placed in the bot- 
tom of the trench and the pipe laid on it. 

All subdrains should be carried to a proper outlet, 
usually connected with the surface drainage system. 
However, as the outflow of the subdrain is rarely heavy 
in volume it may often be carried into adjacent fields 
without causing much damage. The cutting the trench 
and laying the pipe should begin at the outlet end. If 
pipe with bell ends is used, the bell end should be up- 
grade. If the pipe is carried to an outlet through a 
bank, the outer end should be protected by concrete or 
masonry. Care must be taken in filling in the trench 
after the pipe is laid so as not to disturb its position. 
The filling may be of gravel, broken stone, or earth, ac- 
cording to the location and the necessity for a firm 
covering. 

The size of the pipe bears a distinct relation to the 



ROAD DRAINAGE 85 

grade at which it is to be placed. Some road builders 
insist that a grade of at least 5 inches to the 100 feet 
is essential; others claim that 1 inch, or even \ inch 
is sufficient. The most popular practice seems to 
consider that 5 inches is little enough to provide a clear 
flow and avoid chances of settlement which might pro- 
duce a low place somewhere. It must be considered 
that as the water finds its way into the pipe from the 
earth about it, if a sag developed at any point the water 
would be forced out at that point through the same 
openings at which it entered and saturate the base of 
the roadway. 

In figuring the depth of a subdrain the soil must be 
considered first. In clay and other plastic soils a pipe 
or tile drain will drain an area about six times its depth 
on each side. Thus a pipe laid 3 feet deep should drain 
the subsurface water out of such soils 18 feet on each 
side, or 36 feet in all. In more porous soils the dis- 
tance at which the earth is drained is much greater, 
sometimes more than ten or twelve times the depth of 
the ditch. 

Experiments have shown that the earth-water does 
not drain into the subdrains until the water in the entire 
drained area reaches a level, but that the line of drain- 
age is a practically straight line from the pipe to the 
surface of the earth at a given distance. For instance, 
if a certain soil is stated to drain 30 feet to a pipe 3 feet 



86 



PRACTICAL ROAD BUILDING 




(Courtesy U. S. Department of Agriculture.) 

Fig. 10. — This is a photograph of a model made by the 
United States Office of Public Roads and Rural Engineering. 
It shows side-hill drainage, concrete culvert, surface ditch, side 
drain, drop inlet, culvert, V stone drain, side outlet, blind drain, 
center drain, laterals, and cobble gutters. 



below the surface, the 30 feet will be the limit at which 
the drainage is apparent near the surface. At 20 feet 



ROAD DRAINAGE 87 

from the pipe 1 foot of the earth will be drained, and 
at 10 feet there would be 2 feet of dry earth on the 
surface. Taking, then, a road 30 feet wide with a sub- 
drain pipe 3 feet under each side ditch, the subsurface 
water would be drained from the center of the road to a 
depth of li feet, in addition to the height of the crown 
of the road. Except in the most severe climates this 
depth should be sufficient to prevent frost-heaving to 
any appreciable extent. 



CHAPTER V 

ROAD FOUNDATIONS 

The natural earth is the final foundation on which all 
road structures must ultimately rest. Therefore, a 
study of road foundations is a study of the character- 
istics and conditions of the ground, and the methods by 
which a concentrated load on the road surface may be 
distributed over a ground area large enough to carry it 
without damage to the road structure. 

The subject of road foundations is naturally classified 
into two parts: Natural Foundations and Artificial 
Foundations. The natural foundations are those 
which relate to all cases alike — the original earth base 
which must support the entire structure; the artificial 
foundations are those which support the various sur- 
facings which modern traffic demands and convey the 
load pressure to the natural foundations. The Second 
International Road Congress which was held in Brus- 
sels in 1910 presented the following as one of its con- 
clusions : 

"The strength of road foundations should be in- 
creased in proportion as the supporting power of the 
ground decreases." In other words, the weaker the 

88 



ROAD FOUNDATION 89 

natural foundation may be, the stronger the artificial 
foundation must be made. 

In figuring out the carrying capacity of the natural 
foundation there must be taken into consideration the 
soil, the subsoil, and sometimes the geological forma- 
tion. The usual soils are gravel, sand, clay, shale, loam, 
and sometimes marl, peat, and muck. The subsoils 
usually consist of the same or similar materials, but 
often hardened into what is known as "hard-pan," 
and often the subsoil is almost or entirely without the 
element of decayed vegetation, while the surface soil 
may be rich with it. 

Soils are formed by the decomposition or "rotting" 
of mineral, vegetable, and animal matter. By far the 
largest element is the mineral, and comes from the 
breaking down of various kinds of rock during the 
course of ages through wind, water, cold, heat, and, in 
the northern portion of the United States especially, 
through glacial action. 

Scientists state that at some remote age in the past 
the northern portion of North America east of the 
Rocky Mountains was covered by a vast glacier, or 
series of glaciers, forced down from the north; that in its . 
formation it absorbed vast quantities of gravel, rock, 
and other minerals which were carried with it until 
it finally rested, with its southern edge about the Ohio 
River, and approaching the same latitude east and west 



90 PRACTICAL ROAD BUILDING 

from there, not passing southward over the Ozark 
region in Missouri, and reaching the Atlantic a little 
south of the latitude of New York City. We are told 
that most, if not all, of the gravel and boulder deposits 
in this great section of country were carried by the 
glacier, and when it melted the courses of the rivers of 
the region were created and the hills and valleys estab- 
lished. It is a demonstrated fact that much of the 
hard gravel found in most of the Northern States is of 
the same geological formation as rocks which are found 
north of the Great Lakes. 

Gravel consists of small pieces of rock which have be- 
come smooth and rounded by wearing against each other 
or against some other substance. It ranges in size up- 
ward from that of coarse sand, with which it is often 
found mixed, to stones of a size where they are called 
by other names, but with the same general character- 
istics. Cobblestones and boulders and various local 
names are given the larger stones in different localities. 
In the smaller or gravel size the pebbles are often found 
coated with a thin covering of clay, which would sug- 
gest that the water by which it was surrounded at the 
time of its deposit held a large amount of clay in solu- 
tion. 

While these glacial gravels are usually very hard, 
there are vast deposits of a softer gravel over many of 
the Southern States. The scientists have not vet stated 



ROAD FOUNDATION 91 

authoritatively the origin of these gravels, which are 
found in beds on or near the surface. One name given 
to them is the "Lafayette" formation. They compact 
readily, make a good road foundation, and except for 
lack of hardness, to resist wear, would make an excel- 
lent road surface. 

Sand is the name generally applied to any stony-like 
mineral substance which has, by decomposition or 
attrition, broken up or been worn into small particles. 
There are great variations in sands as to size of grain, 
shape of grain, and the mineral elements entering into 
their composition. Practically all sands have more or 
less quartz in their composition. Some sands are com- 
posed of particles which are round, or rounded, like a 
very fine gravel ; others are what is known as "sharp" 
sand, in which the grains are angular. It is the sharp 
sand that is usually specified in all kinds of road work on 
account of its greater stability. Some sand packs hard 
when dry and becomes almost a quicksand when satu- 
rated with water; others, like the sand on many ocean 
beaches, are hard when wet, but are almost impassable 
for vehicles when dry. Even in walking over them the 
feet sink into some dry sands nearly to the shoe tops. 

There are as wide differences in clays as in sands. 
Some clays will dissolve easily in water; others are sol- 
uble only after long immersion. Some will wash away 
easily and quickly, others seem to shed water almost as 



92 PRACTICAL ROAD BUILDING 

if oiled. Only experiments with the local clay in any 
section of country will furnish a safe guide for its use 
in road foundations. A clay subsoil under a marsh, 
however, can generally be depended on, as it has with- 
stood the action of water and moisture long enough to 
demonstrate its reliability. Shale has nearly the same 
component parts as clay. It has evidently become 
hardened by being covered up with earth, and disin- 
tegrates rapidly on exposure to the air and heat and 
cold. 

Loam is a mixture of almost all the various elements, 
but mostly clay and sand. It is found in various shades 
of color and in a variety of consistency when wet. A 
black loam along the Mississippi River bottoms, which 
is exceedingly sticky when wet, is known as "gumbo." 
Marl is a hard clayey substance which has not enough 
lime in it to cause it to harden into limestone. Ex- 
posure to the air has the effect of softening it. 

Peat is vegetable matter which was decomposed 
under water. Muck is earth having a large propor- 
tion of decayed vegetable matter in its composition. 
Neither peat nor muck drains readily, but both dry 
rapidly when the water is removed from about them 
and they are exposed to the air and sun. 

When it becomes necessary, by reason of any pecu- 
liarity of the soil or subsoil which will affect its value as 
a part of the road foundation, to have an analysis made 



ROAD FOUNDATION 93 

to determine its usefulness, samples may be sent to 
the United States Office of Public Roads and Rural 
Engineering, Department of Agriculture, Washington, 
D. C. That office has an adequate equipment and a 
competent force of chemists who will make the exam- 
ination and report without cost at the request of road 
officials. Such a report is very useful, as it shows to the 
local road official just how his local materials can best 
be taken advantage of. 

It occasionally happens, though not often, that a 
section of road has a foundation of solid rock. Such 
instances usually occur in cuts or on side hills. On the 
rare occasions where this condition is found it is only 
necessary to prepare the side ditches carefully, so as to 
provide for the run-off of the water, and then install 
such artificial foundation for the surfacing material as 
the character of the surface may require. 

The first requisite in the preparation of a natural 
foundation on any kind of a subsoil is to see that it is 
well drained; and that the drains will carry off the 
natural rainfall, the excessive storm water, and also 
the water from the subdrainage channels, without per- 
mitting water to settle on or about the road, or the fill, 
or the foundations. 

In sand or clay or loam soils the natural earth should 
be disturbed as little as possible in preparing the nat- 
ural foundations, especially where the factor of sub- 



94 PRACTICAL ROAD BUILDING 

drainage does not require it. Experience has shown that 
much is gained by utilizing the strength of the earth in 
its original position. 

In muck, quicksand, or other soft earth judgment 
must be exercised. Sometimes it becomes necessary 
to dig the muck out and make a fill of stone, brick- 
bats, gravel, cinders, or of hard earth. Previous 
to this, however, test holes should be dug at occasional 
intervals to determine the depth of the muck and its 
character and solidity further down. In some in- 
stances large flat stones have been used as a base to 
prevent the road from settling into the muck. 

The variety of conditions encountered where roads 
cross low, soft places makes necessary more study of 
this phase of natural foundations than the length of the 
roads over them would suggest. But such conditions 
arise frequently and must be considered carefully. 

Occasionally, for a short distance, a condition is 
found where the soft mud or muck seems to have no 
bottom; where load after load of earth and stone and 
other materials have been dumped to create a roadway, 
only to find that the settling goes on regularly, and un- 
der some stress of heavy rain or a melting snow freshet 
the entire road may sink out of sight. For this condi- 
tion the first requisite is a careful investigation to de- 
termine the depth of the soft deposit, which is often 
muck mixed with a quicksand. This may be done by 



ROAD FOUNDATION 95 

building a wooden platform, supplied with windlasses, 
and sinking an iron rod or iron piping until the bottom 
is reached. 

Then it may be necessary to drive a row of piles 
along each side of the road, the piles being close to- 
gether and long enough so that they get a good holding 
in the solid earth at the bottom of the mud. The tops 
of the piles may be held firmly together by planks 
spiked to them. Then the filling may proceed between 
the two rows of piles with any material available until 
a solid embankment is made. 

An unusual treatment of such a condition is some- 
times reported. In one instance a marsh was encoun- 
tered which had given much trouble. It was about 
§ mile across, and the soft mud was so deep that any 
piles that would reach to the bottom would be expen- 
sive and difficult to obtain. In the neighborhood was 
an extensive growth of saplings, ranging from 20 to 40 
feet high and up to 4 inches in diameter at the butt. 

The official in charge built a foundation the whole 
length of the road over the marsh by placing these sap- 
lings in interlaced courses. The foundation was built 
40 feet wide. The first course of saplings was laid cross- 
wise of the road with the butts outward, 6 or 8 inches 
thick. Then a course was laid lengthwise of the road, 
but of slightly smaller saplings, with the butts thrown 
forward to the marsh and the branches on top of the 



96 PRACTICAL ROAD BUILDING 

cross-layer, and the next section of those placed cross- 
wise holding down the butts and branches of those laid 
lengthwise. Then a couple more courses were put on 
until the "mat" of saplings, thoroughly interlaced, 
formed a body approximately 3 feet thick from one 
bank to the other. This was then covered with about 
2\ feet of coarse gravel and opened to traffic. It was 
not considered wise at that time to compact the gravel 
with a heavy roller, but as no considerable settlement 
was observed by the next spring, the surface was 
trimmed with a road machine, rolled, a surface of about 
3 inches of gravel ranging up to f inch in size placed on 
it, and then rolled with a 10-ton roller to a finished 
surface. 

Under a heavy traffic, as traffic is measured on 
country roads, 250 to 500 vehicles a day of all classes, 
this road has shown no material settlement nor any but 
surface deterioration during the three years it has been 
in use. 

In another instance a careful survey of levels indi- 
cated that an entire swamp, over which the road must 
pass, could be partially drained by blasting out a chan- 
nel of less than 100 feet at the outlet of the swamp more 
than half a mile from the road. This was done, and 
during ten months of the year the swamp was compara- 
tively dry; the water level having been lowered nearly 3 
feet. During the dry period the road foundation, made 



ROAD FOUNDATION 



97 



of stone and earth and gravel from higher ground 
cent, became solid enough so that 
it was not affected by the water 
which covered the swamp during 
the month or two of the wet 
season. It may be worth while 
to state, though the fact has no 
relation to road foundations, that 
the owners of that particular 
swamp have formed an organiza- 
tion, and raised the money to 
deepen the outlet and reclaim 
the several hundred acres of 
swamp lands involved, so as to 
make them tillable. 

In some sections of the country 
the natural foundation has been 
used to some extent as the im- 
mediate foundation for the sur- 
facing material. Stone blocks, 
brick blocks, and other surfaces 
have been laid directly on the 
subsoil, with perhaps only a thin 
layer of sand, and have worn 
for many years. Brick has been 
laid on a sand subsoil, and in 
some instances the roads have 

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98 PRACTICAL ROAD BUILDING 

held their shape for several years. The percentage of 
failures of these methods, however, has been so large 
that the methods are not recommended. A new type 
of construction, known as "sand asphalt," has been laid 
directly on the subsoil. These roads have not been 
down long enough to determine either their lasting 
qualities or whether the natural soil furnishes an ade- 
quate foundation. These roads are treated under their 
appropriate heads in other chapters. 

Artificial foundations vary with the conditions of the 
subsoil and the types of surfacing. For macadam roads 
a foundation of broken stone is laid directly on the 
subgrade, which has been properly shaped and rolled. 
Care must be taken in preparing the subgrade that no 
soft spots remain; when such spots appear under the 
roller the soft earth should be removed, and earth which 
will compact firmly put in its place. 

The most approved practice calls for broken stone 
ranging in size from 1 J to 3 inches. This is usually laid 
to a depth of 5 or 6 inches after being rolled, but in 
determining the thickness of the foundation considera- 
tion must be given to the amount and character of the 
traffic the road is expected to carry. On roads where 
much of the traffic is composed of heavy trucks 8 or 9 
inches of stone may be necessary; where the traffic con- 
sists mostly of light pleasure vehicles 4 inches of stone 
have been found adequate for the foundation. 



ROAD FOUNDATION 99 

A practical illustration of this particular feature is 
found in the driveways of the Gettysburg Battlefield, 
many miles in extent. A few of the roads, those form- 
ing the main thoroughfares through the Federal reserva- 
tion, are constructed with foundations 6 to 8 inches in 
thickness; but by far the greater part of the road mile- 
age is built on 4-inch foundations. 

For more than a decade these roads have stood up 
under a very heavy travel of pleasure vehicles and have 
given satisfaction to great numbers of visitors and 
tourists. Only pleasure traffic is allowed except on 
those main thoroughfares which were formerly county 
roads, unless permit is given by the Federal authorities. 

It has seemed necessary that such permits be issued in 
several instances. Usually the necessity arose for the 
purpose of conveying a heavy stone or granite base of 
some monument to the location which had been se- 
lected for its erection. There are many of these monu- 
ments in various places on the battlefield, marking his- 
toric spots or representing the patriotism of other sec- 
tions of the country. 

The bases for these monuments are usually solid 
blocks of stone or granite, weighing sometimes 10 to 
20 tons. To get them to the proper location they must 
be hauled on trucks from the railroad station in the 
village of Gettysburg to the site selected over the roads 
most available. These roads are designated by the 



100 PRACTICAL ROAD BUILDING 

authorities when the permit is given, and provision is 
always made for as large a proportion of the distance as 
possible over the main roads. 

It is the almost invariable experience that the main 
roads hold up, except perhaps in spots, under these 
loads. Almost invariably, also, it is found that when 
the driveways with the lighter foundation are reached 
they are crushed and displaced, requiring practical 
reconstruction of the section of roadway traversed. 

But it has also been found that as a matter of 
economy it is cheaper to reconstruct the roads in these 
occasional instances than it would be to have made the 
foundations heavy over the entire system. These roads 
cost approximately $8000 a mile, with 4 inches of 
foundation and 3 inches of surfacing. Four inches 
more foundation would probably have cost $3500 or 
$4000 a mile additional. The interest on the money 
thus saved would pay for many times the repairs which 
have been necessary. 

In preparing the subgrade for the stone the usual 
custom in the United States is to bring it to the same 
rounded shape as the surface of the road, so that the 
foundation course of stone shall be uniform in thick- 
ness under the road for its full width. Some road 
builders, however, prefer to make the subgrade flat, 
and to make the rounded surface by putting more stone 
in the middle and less on the sides. In a 5-inch founda- 



ROAD FOUNDATION 101 

tion this plan would call for 6 inches of stone in the 
center and 4 inches at the sides, giving the road a 
crown of 2 inches. While this method has been used 
much abroad, especially on English roads with Telford 
foundations, American practice only seems to favor it 
in exceptional conditions. 

One of the arguments favoring the rounded rather 
than the flat subgrade is that the present-day traffic is 
so different from that of former years, especially in the 
weight of vehicles, that a flat subgrade under present 
conditions might soon become settled in the middle, so 
as to be lower at the center than at the sides. In such 
cases moisture might settle under the middle of the 
roadway instead of draining away at the sides, and the 
frost action would prove damaging. The success of the 
flat subgrade abroad, it is argued, is due to the fact that 
for scores of years the stone has been compacted by an 
ordinary traffic no part of which was heavy enough to 
displace the subgrade, until the stone foundations have 
become so thick and so dense that they can be depended 
on to carry almost any load without affecting the sub- 
grade. 

Telford foundations are used where the subsoil is 
soft, so that broken stone would be likely to sink in. 
The Telford foundation takes its name from its in- 
ventor, who was a noted road builder in the south of 
England a century ago. 



102 PRACTICAL ROAD BUILDING 

In putting in a Telford foundation the subgrade is 
usually shaped with a crown the same as the crown of 
the finished road. Stones are then set up edgewise with 
the widest and flattest edge down, and with the longest 
dimension crosswise the road, and the points sticking 
up. The stones are placed as close together as pos- 
sible. The top points are then broken off with a sledge 
and the pieces driven down as wedges betwen the stones. 
This breaking off the tops of the stones brings them to 
a uniform height and the wedging makes them solid. 
The foundation should then be rolled with a heavy roller 
until it is hard and solid. Then it is ready for whatever 
surfacing has been selected. 

It is proper to state in this connection that Telford 
completed his roads by the addition of several inches 
of broken stone. Modern practice, however, makes 
greater use of his foundation than of his completed 
road. 

There is considerable variation in the sizes of stone 
employed in building Telford foundations in different 
states. Connecticut and New Jersey require a depth 
of 8 inches; New York, 6 to 8 inches; Massachusetts, 
5 to 6 inches. The width of the stones as set may reach 
anywhere from 6 to 10 inches in Connecticut; 4 to 10 
inches in Massachusetts and New York, while New 
Jersey uses smaller stones not exceeding 4 inches in 
width. In length, placed crosswise of the road, Con- 



_ 



ROAD FOUNDATION 103 

necticut uses stone 8 to 18 inches long; Massachusetts 
and New York, 6 to 15 inches; and New Jersey, any- 
available length up to 10 inches. In Massachusetts, 
however, 2 inches of gravel is generally rolled into the 
subgrade before the stones are placed. 

Concrete foundations are necessary where brick or 
other blocks are to be used for the surface, and some- 
times when other surfaces are employed. If the traffic 
over the road is to consist mostly of heavy loads, con- 
crete foundations should be placed under most kinds 
of bituminous surfaces. The thickness of the concrete 
foundation must depend on the nature of the subsoil, 
and on the prospective loads to be carried, taken in 
connection with each other. Many road authorities 
claim that the concrete should not be less than 5 or 6 
inches thick; on the other hand, the state of California, 
after careful investigation and tests, is building more 
than 1000 miles of state roads on a 4-inch concrete 
foundation. 

The concrete for road foundations is made either wet 
or dry, according to circumstances. If water is plenty 
most road builders prefer a wet mix; but there should 
not be water enough in it so that there will be any 
material run-off. A dry mix requires more tamping 
so as to get the moisture thoroughly distributed, and 
it should never be so dry that it cannot be tamped into 
a solid mass. At its best, dry concrete is not so dense 



104 PRACTICAL ROAD BUILDING 

as that which is placed wet. A concrete which is a 
medium between a dry and wet mix is used by many 
road builders. This is of the consistency of a stiff 
mortar, just soft enough to be tamped into place before 
it sets. 

On large contracts, or where there is much work to be 
done, it is usually considered more economical to use 
mixing machines. Of these there is a variety, and each 
mixing machine possesses some peculiarity which makes 
it particularly available for some especial work under 
certain conditions. As between "batch" mixers and 
"continuous" mixers a majority of engineers seem to 
prefer the "batch" class; while a large number of prac- 
tical concrete men prefer the "continuous" machines. 
These engineers claim that the batch mixer is more nearly 
"fool-proof," insures a more uniform and thorough mix. 
Some practical men claim that the mixing can be done 
just as well and much faster with a continuous machine 
if properly handled; and that no one has any business 
attempting to mix concrete who does not know how or 
does not know when his product is in the best possible 
condition. Most of the modern mixing machines of 
either class have devices for depositing the mixed con- 
crete in its proper place as a part of the labor-saving 
proposition. 

Hand mixing is done on a mixing platform made of 
planks spiked close together on cross-pieces, either of 



ROAD FOUNDATION 105 

plank or scantling. The sand and cement are first 
thoroughly mixed by turning with shovels, beginning 
at the sides and working toward the center; then revers- 
ing and turning toward the center. When the cement 
and sand are thoroughly mixed the stone or gravel ag- 
gregate is added and the turning is continued until all 
the materials are thoroughly mixed in a dry state, and 
then the water is added. 

If plenty of wheelbarrows are at hand the water may 
be put on the entire batch on the mixing platform; 
the turning and watering and mixing may proceed until 
the concrete mass is properly mixed, and be loaded at 
once on the barrows and deposited in place, raked into 
position, and tamped until the proper density is secured. 
If there are not enough barrows a part of the batch may 
be watered and mixed at a time, and another lot mixed 
while the first is being taken away, all depending on 
the size of the batch and the rapidity of removal. 
Care must be taken in such cases to see that there is 
no wait long enough for the first set of the concrete to 
take place before the next delivery. 

Concrete in road foundations should not be laid when 
the temperature is within 10 degrees of the freezing- 
point. At night, in any weather, the end of the work 
should be covered with tarpaulins and kept wet. The 
foundation itself after it has set should be covered with 
sand or dirt to a depth of 2 or 3 inches and kept moist 



106 PRACTICAL ROAD BUILDING 

for a period ranging from three days to a week, so that 
the final set may take place without damage. Some 
road builders make a practice of setting a board up 
edgewise at the end of each day's work and making an 
expansion joint. While many good authorities hold 
that expansion joints are not necessary in foundations, 
others hold that it is better to provide them than to 
run the risk of cracks where one day's fresh concrete 
meets that which was placed the day before. 

The mineral aggregate of the concrete for a road foun- 
dation should be of broken stone or gravel, clean and 
free from dirt, and especially free from clay. Old 
stone, which has been used in macadam roads or other- 
wise, does not make a satisfactory aggregate for con- 
crete. Fresh stone with clean sides, showing fresh 
breaking, is best. In the use of gravel, if the gravel be 
not perfectly clean, as in most cases of bank gravel, it 
should be washed. Creek or river gravel does not 
usually need washing; but care must be taken to see 
that it is well graded; that is, that there is a proper 
proportion of different sized stones. 

Stone or gravel as the aggregate for a road foundation 
does not require the hardness or strength that is neces- 
sary in road surfaces, especially if the subgrade be of 
reasonably firm earth. Almost any available material, 
properly prepared, will answer the purpose. There are 
patented preparations by means of which foundations 



MM 



ROAD FOUNDATION 107 

have been made of the natural soil, loam, sand, etc., 
and Portland cement. With the proper chemical pro- 
portions there seems no reason why such mixtures 
should not prove permanent. 

(Detailed information on this subject may be secured 
from the United States Office of Public Roads and 
Rural Engineering, Department of Agriculture, Wash- 
ington, D. C.) 

Concrete foundations should never be placed on an 
old macadam or gravel base, which has been built up 
and worn down by years of travel. The reason for this 
is that it is practically impossible to get the concrete top 
and the old base joined firmly enough so that water 
will not get in between; then the frost breaks up the 
concrete. Besides, the old macadam or gravel base is 
usually fully as solid and firm as new concrete would be. 
Repair of defects or correction of alignment may be 
made in the usual way, by roughening the surface, and 
using fresh stone with a cement grout or soft mortar. 
Sometimes an entire old macadam or gravel foundation, 
after having been scarified, repaired, and rolled, may 
be made uniform and solid by an application of a 
cement grout, probably al:loral:lJ mix, which will 
fill all the voids or interstices and make a thoroughly 
solid foundation. 

Much, however, depends on the surfacing material 
which is to be placed on the foundation. These are 



108 PRACTICAL ROAD BUILDING 

treated in the Second Part, under the various headings 
of ' 'Roads." Generally speaking, old stone or gravel 
foundations are more economically used when employed 
as bases for bituminous surfaces. One reason for this 
is that the bituminous surface fits closely into the small 
irregularities of the foundation, and leaves no space for 
water to settle; second, it is more nearly waterproof 
than other surfaces; and third, that the expansion and 
contraction due to heat and cold does not pull it loose 
from the foundation. 

Notwithstanding the theories of some engineers, there 
is no economic sense in digging up or destroying an old 
gravel or mac'adam foundation. Such a foundation, 
settled and compacted by years of traffic, represents a 
certain definite investment for the community; and its 
destruction is a waste of community funds. In such 
cases the study should be for the surface best adapted 
to the existing foundation, as the foundation should 
represent at least half, usually more, of the value of the 
completed road. 

In some cases where the subgrade presented irregu- 
larities and unevenness as to density, concrete slabs 
have been used as foundations. Sometimes these 
slabs have been reinforced by expanded metal or heavy 
wire mesh. The slabs range from 12 to 20 feet in 
dimensions and are about 6 inches thick. The sub- 
grade is prepared as carefully as possible, the slabs set 



ROAD FOUNDATION 109 

close together, and the joints filled with cement grout. 
Usually a sand cushion of 3 or 4 inches is placed on the 
subgrade under the concrete slabs. 

A paving company manufacturing a patented pave- 
ment has at times employed its surfacing methods in 
constructing foundations. This method, which is 
understood not to be patented as to foundations, con- 
sists of placing- broken stone or gravel to the proper 
depth and pouring grout over it while it is being rolled. 
The grouting and rolling continues until all the voids 
are supposed to be filled, and then the work is left to set 
in the usual way. Especial care must be exercised in 
using this method to stop the rolling before the first 
set of the cement has begun; otherwise the strength and 
holding power of the cement will be interfered with. 

Foundations of bituminous concrete, using asphalt or 
tar instead of cement, with broken stone or gravel, 
have been laid. Reports show that while serviceable, 
they have not the strength of Portland cement concrete, 
and that the only special reason for their use would be 
their cheapness in some given locality. In any remote 
place where cement is especially expensive by reason 
of freights or otherwise, and tar or asphalt cheap 
because of local production, the bituminous materials 
can be depended on to make a foundation which will 
last for many years under proper conditions. 



CHAPTER VI 

ROAD SURFACES 

The surface of a road must be considered in connec- 
tion with the grade; with the smoothness; with the 
traction power required to pull loads; with the use of 
the road either for pleasure vehicles or for heavy truck 
traffic; and with its permanency or "staying" qualities 
under different conditions of traffic and climate. 

The surfaces of standard types of roads are described 
under the various chapters relating to the construction 
of those roads. Modern practice, however, has a tend- 
ency to depart from types to the extent of putting almost 
any kind of a surface on almost any kind of a founda- 
tion in the effort to get the best road for the least 
money. Sometimes experiments along this line have 
been very successful; in other instances they have 
been wasteful — if not total failures. 

As to grade and traction power. As automobile 
trucks are so constructed as to go over any ordinary 
grade, horse-power must be the basis for figuring. 
According to the conclusions which have been reached 
by engineers who have studied and experimented on the 
subject, a horse will draw four times as much load- 
no 



ROAD SURFACES 111 

weight on a level as it can draw up a 10 per cent, grade. 
For instance, if a team of horses can draw a load of 
3000 pounds on a level road, the same amount of pulling 
would draw 1500 pounds on a grade ranging from 5 to 6 
per cent., and 750 pounds on a 10 per cent, grade. 

Or, to put it the other way: If two horses can pull 
3000 pounds on a level, it will require four horses to 
pull it up a 5 per cent, grade, and eight horses to pull it 
up a 10 per cent, grade. 

The amount that a horse can pull, of course, on a 
level or any grade depends on the smoothness or lack 
of smoothness of the surface of the road. If the sur- 
face of the road be hard and smooth, theoretically it 
would require as much power to haul a load up a 10 
per cent, grade as the combined power required to haul 
it 100 feet on a level and to lift it 10 feet. If the sur- 
face be rough the additional power required must be 
gauged by the degree of roughness. 

It is usually stated that an average draft horse exer- 
cises a pulling power of about 180 pounds, and that this 
can be increased at times, and for brief periods, to 500 
pounds. These periods of special pull are exercised in 
starting the load and may be employed in such emer- 
gencies as make extra pulls necessary; as in defective 
spots or holes in the road; or an especially steep short 
hill which can be covered in a few minutes by putting 
forth the extra energy of which the horse is temporarily 



112 PRACTICAL ROAD BUILDING 

capable. The physical proposition might be compared 
to that of a man, who might be unable to carry a weight 
of 50 pounds for eight hours, but could carry 200 pounds 
for fifteen minutes. 

In connection with the pulling power of horses must 
be considered not only the easy movement of the load 
on wheels, but the foothold of the horses. Where the 
surface is smoothest the power required to move the 
load is naturally least. At the same time the foothold 
of the horse becomes less as the surface becomes smooth. 
On an earth or gravel road the horse may have a better 
foothold, and therefore a greater pulling power; while 
on a smooth, hard surface, such as concrete or asphalt, 
the foothold will not be so firm, and the power neces- 
sary to pull the load will be correspondingly less. 

Up to a certain grade, however, the authorities all 
favor the smooth road; but as to just where the smooth 
surface becomes a disadvantage and the rough surface 
an advantage there is much difference of opinion. 
Some assert that 7 or 8 per cent, grades are as steep as 
smooth hard surfaces should be built; others claim that 
a rough surface is more economical from a 10 per cent, 
grade up; while in various localities throughout the 
country, notably in Allegheny County, Pennsylvania, 
hard smooth surfaces are used on grades as steep as 
14 per cent. 

One fact may be noted. When smooth, hard roads 



ROAD SURFACES 113 

are built in country districts it requires a little time 
for farm horses to get accustomed to them so that they 
can exercise their full draft power. With care in 
driving, however, they soon adjust themselves to the 
new conditions, and become as sure footed as horses 
trained to city pavements. 

The Massachusetts Highway Department has made 
many experiments in surfacing roads on various kinds of 
foundations and in maintaining the surfaces in good 
travelable condition. The reports of these experiments 
are voluminous and range from official reports to papers 
and addresses delivered before scientific and other con- 
ventions and published in magazines and official pro- 
ceedings. They range all the way from the application 
of oil on a graded earth road to patching cracked con- 
crete with tar or asphalt. 

While each particular road presents a different condi- 
tion, the approved Massachusetts plan for creating a 
wearing surface on a road, whether it be an earth road, 
a gravel road, or a macadam road, is to make such an 
application of asphaltic material, with a sand, or fine 
gravel, or stone-chip covering, as will produce a mat or 
carpet which will take the wear, shed the water, and 
protect the road from damage. This surfacing is 
patched or renewed whenever it is necessary to main- 
tain the road. Traffic conditions in that state require 
that the roads be kept in good condition. 

8 



114 PRACTICAL ROAD BUILDING 

The asphaltic material used varies. In some in- 
stances light asphaltic oil — 45 per cent, asphalt — is 
first used at the rate of § to 1 gallon per square yard. 
That is to get the proper penetration. Afterward more 
light oil may be used in smaller quantity, or a heavy oil 
— 60 to 65 per cent. — may be added, and the surface 
covered with fine gravel, sand, or stone chips. After 
the surface has been established, one application of the 
heavy oil each year is sufficient in most cases; but, of 
course, the amount, and the grade of the asphaltic oil, 
and the frequency of its application are matters which 
depend entirely on local conditions of climate, soil, 
foundation, and traffic. 

In maintaining these surfaces the automobile with 
pneumatic tires is one of the greatest factors to be 
considered. Trucks with steel tires easily damage 
this road surface if there are no automobiles. Motor 
trucks with solid tires do less damage; but the pneu- 
matic automobile tires are a positive advantage to the 
road, ironing and smoothing out the surface which may 
have been cut up by other vehicles. It has been stated 
that it is cheaper to maintain a perfect surface of this 
character under a travel of a thousand automobiles a 
day than under that of fifty loaded wagons with steel 
tires. On the other hand, the fifty loaded wagons will 
do little damage if three hundred to five hundred auto- 
mobiles with pneumatic tires are going over the road at 



ROAD SURFACES 115 

the same time, as they smooth out most of the irregu- 
larities caused by the heavy loads on the steel tires. 

But with an earth base, especially if the earth be of a 
soft character, easily permeable by water, the surfacing 
is likely to be cut through and rutted or holes devel- 
oped at any time a heavy rain occurs. The asphaltic 
top only protects the road underneath to the extent that 
it makes it smooth and waterproof under ordinary 
conditions. When the conditions change, other or 
further methods are necessary. 

When a road surface has been treated with asphaltic 
oil, especially with heavy oil, the surface particles be- 
come coated with the asphalt. If the surface becomes 
broken up and rutted by the travel, the road can be 
shaped again by the road machine or the road drag, and 
the particles will amalgamate together and the surface 
will resume its former condition, especially if there have 
been several applications so that the surface material 
has been thoroughly saturated with the oil. It must 
always be remembered, however, that when water gets 
under the surface, and the traffic breaks through, it 
requires but few vehicles passing over the spot to make 
a mud-hole; and a mud-hole or other break in the sur- 
face must have prompt attention to prevent its expan- 
sion to a really "bad place in the road." 

It is a general impression, under average conditions, 
that with a fairly good foundation it is more economical 



116 PRACTICAL ROAD BUILDING 

to maintain a good surface than to let the original sur- 
face wear out and build a new one. In many instances 
where the traffic has increased from an average of fifty 
vehicles a day of all kinds to more than three hundred a 
day — the increase being mostly in motor vehicles — good 
wearing surfaces have been maintained at a compara- 
tively small expense per year for ten or twelve years. 
As every road surface, new or old, needs constant at- 
tention, the question of cost of upkeep must be the 
difference between the cost of repairs on a new road and 
on an old one. 

A 15-foot road has 8800 square yards of surface to the 
mile. Unless the traffic be very heavy, or unless the 
traffic changes in character rapidly, a new hard surfaced 
road should be kept in good condition for the first three 
to five years at an expense of not more than 2 to 5 cents 
a square yard; that is, from $176 to $440 per mile. 
The experiences of various highway departments have 
shown that the cost of repairs gradually increases as the 
road grows older. These increases in cost, however, are 
invariably shown to be due to the fact that there has 
been a very great increase in the traffic. In this con- 
nection it may be well to state that according to the 
most careful estimates the vehicles traveling over the 
roads of the United States considerably more than 
doubled between the years 1910 and 1915. 

It has been figured out quite carefully that when the 



ROAD SURFACES 117 

cost of keeping a "mat" or "carpet" surface — as pre- 
viously described — in good condition exceeds 10 or 
12 cents a square yard per year, it is more economical 
to build a new road of a character and type which will 
stand the traffic. The basis of the calculation is the 
cost of making the new road, or such part of it as must 
be rebuilt. If the yearly interest on the cost of recon- 
struction be less than the annual cost of maintaining 
the old road, it is more economical to rebuild the road. 
This is especially true by reason of the fact that the 
new road should be built to withstand the stress of 
present and future travel, the constant growth of which 
would make the repairs of the old road constantly and 
rapidly increase in cost. 

The United States Office of Public Roads began about 
1908 or 1909 to make experiments in regard to various 
materials and methods of road surfacing, both on its 
own account and in connection with other interests. 
These experiments relate both to dust suppression and 
road preservation. They were made in various parts of 
the United States and under greatly varying conditions, 
and the various bulletins issued by the Department 
of Agriculture, which are obtainable by any road 
official, give in detail the character and location of 
the experiments and the successes or failures which 
resulted. 

It must be borne in mind that until 1907 or 1908 



118 PRACTICAL ROAD BUILDING 

the macadam or broken stone road (described in another 
chapter) was considered the highest and most nearly 
permanent type of construction applicable to country 
roads. Its successful use for one hundred and fifty 
years in France, and for nearly one hundred years in 
England, and for only triflingly shorter periods in the 
German and Scandinavian countries, and the employ- 
ment of the same principle in the United States on the 
most highly improved roads, had established that form 
of construction as standard. 

The advent and rapid development of automobile 
travel between the years 1900 and 1906 seriously inter- 
fered with the road surfaces. It was found that the 
previous methods of maintenance would not keep the 
roads in good condition. The first official notice of 
this deterioration of the roads under automobile traffic 
in this country was in the Annual Report of the Massa- 
chusetts Highway Department in 1907. Although the 
damage had been noted in other states, it had not been 
made a matter of official report. 

So universal throughout the civilized world was the 
condition which threatened the destruction of broken 
stone roads that an International Road Congress was 
held in Paris in 1908 to determine what measures were 
necessary to preserve the roads, and the wisdom of the 
highway engineres of all civilization was brought to 
bear on the subject. Another International Road 



ROAD SURFACES 119 

Congress was held in Brussels in 1910, and the third in 
London in 1913. 

In the earlier stages of the extraordinary wear on the 
roads the damage was attributed entirely to automo- 
biles, largely because it had not existed prior to the use 
of automobiles. Study of the subject, however, de- 
monstrated that it was the combined effect of steel- 
tired and pneumatic-tired vehicles which produced the 
destruction. The excellence of the surface of a broken 
stone road is due to the fact that the steel tires and steel- 
shod hoofs, while grinding some dust and small particles 
from the stone, packs that dust and fine particles down 
between the stones, forming at once a binder for the 
surfacing stone and a coating which prevents rapid 
wear. The rains, by washing the dust further down 
among the stones, aided in forming a hard, smooth sur- 
faced, substantial road. 

Then the automobile came with its pneumatic tires 
and low, rapidly moving body. The suction created 
by the passing of the machine over the road pulled the 
dust out of the crevices between the stones and threw it 
into the air to be blown away by the winds. Then 
horses and steel tires would break down more of the 
surfacing stone, the particles to be blown or thrown off 
as before. This alternate breaking and throwing off 
rapidly destroyed the best stone road surfaces. 

For a time much attention was given to dust sup- 



120 PRACTICAL ROAD BUILDING 

pression as a cure for the evil. A number of materials 
were invented or developed for keeping down the dust 
which have been more or less successful, according to 
the intelligence with which they have been applied. In 
a large number of cases they have been very successful, 
especially on roads where the traffic did not increase to 
an extent beyond their usefulness. 

It was soon found, however, that the suppression of 
the dust — keeping it down so that it would not fly in 
the air — did not produce satisfactory results on heavily 
traveled roads. Dust continued to form under the 
traffic, and though so loaded with tar or oil or chemicals 
that it would not fly in the air, it was unpleasant to 
travel over, and formed a very offensive mud after 
rains. 

Then the experimentation turned to road binders and 
preservatives, so as to develop or discover methods of 
constructing road surfaces so that they would wear well; 
would produce but a small amount of dust; and as far 
as possible pack the dust again into the surface as an 
additional prevention against wear. Another class of 
experiments have been along lines of creating a surface 
so hard that the wear will be negligible, as is claimed 
for various modifications of Portland cement concrete. 
Several of the surfaces thus invented or developed have 
been patented and are known under trade names 
which can be found in any current copy of journals or 



ROAD SURFACES 121 

magazines devoted to road improvement. Usually, 
each of such materials as are used and the methods of 
application may be depended on to produce satisfac- 
tory results under conditions favorable to their employ- 
ment. It will be wise, however, for a road official to 
carefully study the relative conditions where any such 
surface has been successful, and those of the road under 
his control which he desires to improve. 

Resiliency in a road surface has for many years been 
considered necessary, and still is so considered in many 
sections of the country. Resiliency is that quality in a 
road surface which is the opposite from rigid. A resil- 
ient surface "gives" to some extent under the impact 
of traffic. All bituminous surfaces are resilient; as are 
also, though to a less extent, brick and other blocks 
laid on a sand cushion. Concrete is rigid and presents 
an absolute resistance to the impact of traffic. 

The theory is that a rigid road surface is injurious to 
horses and that it causes greater wear on automobile 
tires. This theory is disputed by advocates of concrete 
road surfaces, who contend that the horse becomes ac- 
customed to a rigid surface as readily as to any other 
hard surface, and that the effect on rubber tires is favor- 
able rather than otherwise. There is room for dis- 
cussion on both sides of the question. It appears to be 
a fact that such popularity as rigid surfaces have 
achieved has been in the localities where motor traffic 



122 PRACTICAL ROAD BUILDING 

predominates; and that horse owners, almost without 
exception, prefer road surfaces in which there is some 
resiliency or "give" when the horses' feet strike it. 

Road builders must keep in mind the fact that the 
same materials and methods of application produce 
different results in different sections of the country. A 
certain patented surface which involved a mixture of 
bituminous materials with a concrete surfacing was an 
entire success in one section of Illinois, and a positive 
failure in a locality where it was tried in Ohio. The 
same pavement, while maintaining its strength on one 
of the drives of Central Park in New York City, became 
so unsightly, by reason of the surface "peeling" in spots, 
that it was covered with asphalt by the park authori- 
ties. The patented road made an excellent foundation 
for the well-tried surfacing, but the combination was 
somewhat expensive. 

One eminent engineer has asserted that water, 
properly applied, is the cheapest and best method of 
keeping down the dust and protecting the road surface. 
Possibly his views may be modified by a consideration 
of .the cost of getting the water to the road. His view, 
as expressed, is that applications of water, applied with 
sprinklers during a season, in such quantities and at 
such intervals of time — whether once a day or five times 
a day, as shall keep the road moist, neither dusty nor 
muddy — can be made at less cost than applications of 



ROAD SURFACES 123 

bituminous or other chemical materials which will pro- 
duce an equally satisfactory result. 

Experience does not bear out this theory in the opin- 
ion of most road officials who have tried it, except in 
those cases where water is unusually convenient, so 
that sprinkling wagons can be loaded at practically any 
point along .the road and with practically no expense. 
Such a condition is very unusual. In most cases where 
the road surface suffers most from the creation of dust 
an ample water-supply is difficult or expensive to reach. 

On roads of ordinary traffic, not exceeding two hun- 
dred to two hundred and fifty vehicles a day of all 
classes, and without especially heavy trucks, oiled or 
tarred surfaces have been applied frequently within 
recent years, and when properly applied, with a fair 
measure of success. In almost numberless instances 
the application has been made by persons either with- 
out knowledge, or with fragmentary information, of the 
proper methods. These have resulted in dissatisfaction 
and unpleasant experiences. 

Oil or tar should not be placed on a road until the 
surface has been swept clear of dust. To put bitumin- 
ous materials on top of a coat of dust is to create a con- 
dition where the wheels of vehicles will pick up the 
bituminized surface, leaving the roadway bare in spots 
and clogging the wheels of the vehicles; and footsteps 
of persons or animals will be tracked to the sidewalks 



124 PRACTICAL ROAD BUILDING 

and to adjacent buildings, carrying the marks of the 
bituminous material. 

When such a surface is to be applied, the road should 
be swept clean of dust first with reed brooms, and then, 
if it be a well-bound stone road, with ordinary house 
brooms. Then the oil or tar may be applied, but always 
when the road is entirely dry. 

There are several methods of application. A dozen 
or more different machines have been designed for this 
work, some of which are motor driven, some horse- 
drawn, and some pulled by hand. Some simply deposit 
the material on the roadway; others distribute it under 
pressure. Some are arranged to heat the material; 
others for delivery cold. The availability of either 
method depends on local conditions. 

Some of the bituminous materials, whether oil or tar, 
when rightly applied and covered with a coating of 
stone chips, gravel, or coarse sand, may be opened for 
traffic within a few hours — perhaps the next day. This 
is especially the case where the application has been of 
a light oil, or an oil which has been applied hot, and in 
small quantity per square yard. 

According to some road builders, to secure the best 
results, a light oil should be spread on the dry, swept, 
surface of the road, using about J to J gallon per square 
yard. This application should be left for twenty-four 
or forty-eight hours without covering, and without 



ROAD SURFACES 125 

traffic, to allow the oil to sink well into the road sur- 
face. Then a similar amount of heavy oil should be 
applied, and the covering of sand or stone chips put 
on. If the heavy oil is applied hot, about 212° F., the 
road may be opened for traffic after six or eight hours. 
If the application is of heavy oil cold, at least twenty- 
four hours should elapse before traffic is permitted. 

Some materials, especially some classes of tars, re- 
quire that the road be kept closed to traffic for a week 
or more to give the material time to "set"; that is, 
to become hard enough so that it will not be picked up 
from the road by the traffic, and that it will not be 
tracked to adjacent walks and buildings. 

When oil is to be heated it is usually shipped in tank 
cars which have steam radiating pipes, so that attach- 
ment may be made with a steam roller or any other 
steam-producing machine. Sometimes a car can be 
switched near enough to some local plant operated 
by steam pow T er so that a steam hose may be at- 
tached to the radiators of the car. If the material is 
sufficiently heated in the car, and the distribution be 
prompt, it will probably not require further heating. 
However, there are a number of distributing machines 
on the market which have heating apparatus as a part 
of their construction. When shipped in barrels, the 
material may be heated in wheeled kettles at the road- 
side. 



126 PRACTICAL ROAD BUILDING 

An eminent authority on highways (Professor Arthur 
H. Blanchard, of Columbia University) presents the 
following table of costs of what he considers an average 
condition: The road was treated with \ gallon of 
heavy asphaltic oil, in two applications of \ gallon 
each, per square yard. The average haul was 2 miles 
for the oil and 2| miles for the sand. No allowance is 
made for use of machinery or for profits to contractor, 
the work having been done on force account. The 
detailed costs per square yard are given as follows: 

Cleaning and sweeping $0.0056 

Patching old surface 0016 

Cost of oil 0319 

Heating oil .0031 

Delivering oil 0038 

Distributing oil 0029 

Furnishing sand at side of road 0165 

Spreading sand 0073 

Watering 0012 

Rolling 0002 

Supervision 0025 

Total $0.0766 

It will be noted that nearly one-half the cost of the 
surfacing was the cost of the oil. The price of labor was 
$1.75 per day of eight hours. 



ROAD SURFACES 127 

• 

Some experiments have been made in which the sand 
was heated; but the reports do not seem to show a suffi- 
cient degree of additional excellence to recommend the 
extra expense. 

With ordinary traffic a road such as the one described 
should require but a single application of J to J gallon 
of heavy oil each subsequent year, with the usual sand 
covering, to keep it in good condition indefinitely. 



CHAPTER VII 

ROAD BRIDGES AND CULVERTS 

The greatest amount of water ever likely to pass 
under a bridge or through a culvert must be the meas- 
ure of its size. On large streams this may be figured 
from past high-water records; on medium and smaller 
streams the number of acres or square miles drained, 
and the heaviest known rainfall or the heaviest snow- 
fall followed by quick melting may be figured out to 
determine the greatest flow. If there is a railroad 
bridge over the same watercourse near by, it is prob- 
able that the engineering department of the railroad has 
a carefully worked out estimate of the stream flow. 
Nearly all railroad companies furnish these figures to 
highway officials on request. They are obtained by a 
survey of the drainage area. The heaviest rainfall and 
the steepness of the slopes are the other principal 
factors. In some cases springs and flowing wells are 
numerous enough to be taken into consideration. 

It is most important from every standpoint that 
the waterway be large enough to carry off the water 
without obstruction. Thousands of bridges have been 
washed away and an almost limitless number of cul- 

128 



ROAD BRIDGES AND CULVERTS 129 

verts washed out by the neglect of this primary prin- 
ciple. 

In addition to securing data covering the extreme 
high water and low water for a long period of years, 
allowance must be made for the obstruction by piers 
and abutments, especially when a number of short 
spans are to be built across a wide channel. Most 
bridge experts and engineers hold that even though a 
considerable amount be added to the expense of the 
bridge, it should be built with water-way openings 
enough and large enough so that there shall be no hold- 
ing back of water, but that the run-off must be perfectly 
free. 

Culverts are generally divided into three classes : the 
pipe, box, and arch. Pipe culverts include those con- 
structed of vitrified clay, cast iron, corrugated metal, 
and sometimes of concrete. Box culverts are built of 
concrete, stone, and wood. Arch culverts are usually 
built of concrete, reinforced or otherwise, stone, and 
brick. The selection of the type of culvert for any given 
locality should be based on the availability of materials 
and the economy of construction, although the size of 
the opening and the depth below the road surface are 
factors which must be considered. 

The culvert, in addition to its function in carrying off 
water, must sustain the weight of the roadway above it 
and of the loads which go over the road. When the 

9 



130 PRACTICAL ROAD BUILDING 

culvert is at a considerable distance below the road sur- 
face, say 4 or 6 feet or more, the pressure on it from loads 
is more evenly distributed than where it is within a foot 
or two of the surface. When it extends near to the 
road surface the culvert is likely to get the direct press- 
ure of the load when the wheels pass over it, and con- 
sequently it must be of sufficient strength to carry the 
load without breaking or collapsing. In the employ- 
ment of pipe culverts, where the embankment is not 
high enough to properly protect a large pipe, many road 
officials have put in a row of two or three or more small 
pipes side by side, either close together or separated 
a few inches, according to circumstances. For instance, 
three 12-inch pipes will usually answer all the water- 
carrying purposes of one 24-inch pipe, and will give an 
additional foot of embankment over them which, if 
the pipes be separated somewhat, will materially reduce 
the pressure from heavy loads. 

Except in occasional instances it is hardly necessary 
to go into a detailed investigation of the load-carrying 
strength of pipe culverts. Most of those on the 
market have been so widely used, and under such vary- 
ing conditions, that if properly placed they are likely 
to withstand the pressure from any loads they may be 
called on to carry. 

The concrete pipe, which is not as generally known as 
the other types, has many advocates among those who 



ROAD BRIDGES AND CULVERTS 131 

have used this type. Where the material is convenient 
and available these culverts are said to cost about one- 
fourth the cost of cast iron. They are made in molds, 
and in sections 4 to 8 feet in length, according to size. 
They are similar in some respects to vitrified clay pipe 
except that they do not have the bell and spigot joint, 
but are made with square or beveled ends. When 
placed in position the joints, after being brought to the 
closest possible contact, are covered with a layer of 
cement mortar. 

In most instances where concrete pipe culverts have 
been used the county or township has established a 
central plant, purchased molds, and in rainy weather or 
at other slack periods put in the time making the con- 
crete pipe for future use. 

Vitrified pipes for culverts are made in various sizes 
ranging from 12 to 36 inches and in sections 2 feet long. 
In laying these sections the bell end of the pipe should 
always be up stream, and the best authorities claim 
that the top of the pipe should be at least 15 inches 
below the surface of the road. A greater depth is 
desirable, especially if the road carries heavy loads, 
such as traction engines or other vehicles with heavy 
wheel pressure. 

Cast iron pipe is usually made in 12-foot lengths. 
Quite recently, however, cast iron pipes have been put 
on the market in 4-foot lengths. The standard pipe is 



132 PRACTICAL ROAD BUILDING 

uniform in thickness of shell and weight per foot, ac- 
cording to size of the pipe. The new cast iron pipe 
has a thinner shell, is lighter in weight, and is reinforced 
with projecting ribs. While the standard pipe has been 
in use many years, the new pipe may or may not fulfil 
the requirements. Standard cast iron pipe is very 
strong and may be placed within 6 inches of the road 
surface without danger of damage under any ordinary 
conditions. 

Corrugated metal pipe culverts are made in a variety 
of sizes and of different metals, principally wrought iron 
and steel. The wrought iron is held to be the more dur- 
able, being less likely to damage by corrosion. Its 
weight is about one-twentieth that of cast iron, which 
fact applied to freight rates determines its availability 
in many cases. At the point of manufacture it costs 
about the same as vitrified pipe, the difference between 
them in price in any locality depending mostly on the 
cost of transportation. The vitrified pipe weighs sev- 
eral times as much as the corrugated metal. 

Both the up-stream and down-stream openings of 
pipe culverts should be protected by face walls of con- 
crete or of stone or brick masonry laid in concrete mor- 
tar. The face wall at the up-stream or entrance end 
should be so shaped and placed as to lead the water 
naturally into the pipe, and so as to prevent the possi- 
bility of the water getting around or under the pipe to 



ROAD BRIDGES AND CULVERTS 133 

cause a washout. The face wall at the outlet or down- 
stream end should protect the embankment from wash 
and consequent caving, and should also prevent seep- 
age back under or around the pipe, which would be sub- 
ject to the destructive action of frost. Neglect of this 
precaution has ruined many sections of roadway and 
made expensive repairs necessary. 

In laying pipe culverts it is important that the bed 
be properly prepared. The beds at joints are es- 
pecially important, as any settlement will throw the 
pipe out of a true line, and probably cause a leak 
which is likely to undermine the culvert and the 
roadway. If concrete is being used on the job, or is 
convenient, it is well to make a concrete bed for the 
joints. Otherwise a flat stone, thoroughly imbedded, 
or earth so thoroughly rammed down as to be prac- 
tically solid may answer the purpose. After placing 
the culvert the earth should be thoroughly tamped 
under and around the pipe. For this purpose sandy 
gravel is preferable if it can be procured readily. 

The slope at which a pipe culvert should be laid de- 
pends much on local conditions. It should always be 
steep enough, however, so that the culvert will be self- 
cleaning and that no sediment shall remain in it. Cul- 
verts which are smooth on the inside require less slope 
than corrugated metal, the corrugations having a tend- 
ency to retard the flow and thus permit the deposit of 



134 PRACTICAL ROAD BUILDING 

sediment. Generally 1 inch in 5 feet is as slight a slope 
as should be provided, while twice that, or 1 inch of 
decline to 30 inches of distance, will be better. 

Box culverts are made of two side walls and a cover- 
ing over the top. If the side walls be of stone they 
should be of sufficient thickness so that the earth 
pressure from back of them will not force them out of 
position. Where the walls are of concrete they are 
usually made 4 to 8 inches thick, depending on the 
height, and are set into the ground a distance of 18 to 
24 inches below the bed of the stream with a footing of 
about twice the width at the bottom. Only in large 
culverts is it considered necessary to put reinforcing 
material in the side walls. 

If the soil be of a character that is easily washed out, 
a bottom, or floor, should be made. This may be made 
of flat stones carefully fitted together, or of cobbles set 
closely, or of concrete. If, however, the bottom of the 
stream is hard it is often unnecessary to put in any arti- 
ficial bed. It often occurs that a culvert is built over 
a small stream in which for years there had been no 
material change. In such cases there seems no good 
reason why any expense should be incurred in the con- 
struction of a floor. When a concrete floor is neces- 
sary, concrete side walls need only be carried to the 
bottom of the floor. 

The top of a box culvert may be of stone slabs, or 



ROAD BRIDGES AND CULVERTS 135 

concrete slabs placed on iron I beams, or of reinforced 
concrete slabs. In case of large culverts the reinforced 
concrete slabs are usually supported by I beams. These 
slabs are made 6 inches thick and the reinforcement 
may be of any one of several approved types. The 
concrete mostly used is either a 1:2:4 or 1 : 2\ : 5 
mixture, and the slabs should season well before being 
subjected to heavy loads. 

The wooden box culvert should not be built except in 
localities where it is the only available material. It is 
the most expensive of all culverts to maintain, and its 
tendency to get out of order on account of loose planks 
and other defects produces a definite and grave danger 
to traffic. Its use can at any time only be justified as a 
temporary expedient. 

Arch culverts, whether of stone, brick, or concrete, 
are built over an arch form of whatever shape of open- 
ing may be desired. Unless the bed of the stream be of 
exceptionally firm material it is usual to put in a floor 
the width of which is sufficiently great so that it will 
carry the side walls. Stone and brick are laid in ce- 
ment mortar and the masonry properly keyed. 

In building concrete arch culverts most highway 
officials provide themselves with collapsible iron forms, 
which greatly reduces the expense when there is any 
considerable number of culverts of a similar size to be 
constructed. There are several of these collapsible 



136 PRACTICAL ROAD BUILDING 

forms on the market. They are set in proper position 
either on the stream bed or the culvert floor. The side 
forms for the concrete are built of wood in the usual 
manner and the concrete placed and tamped into 
position until the arch form is covered to the required 
depth. As soon as the concrete has set, the arch 
form is collapsed and withdrawn and is ready for use 
elsewhere. 

In this type of culvert some road officials use rein- 
forcement and others do not. The question seems to 
be as to whether it is more expensive to put in reinforce- 
ment and make the walls and arch thinner, or use more 
concrete and do without the iron. It is probable that 
in regions where excessive frost is encountered it may be 
safer to use reinforcement. In other cases it does not 
seem necessary. A design of arch culvert much used in 
Massachusetts is without reinforcement and has given 
universal satisfaction. 

All culverts should have adequate face walls and wing 
walls to protect the embankment and to prevent water 
from getting behind the culvert walls. The face walls 
should be carried down at least 2 feet below the bed of 
the stream, and lower than that if the soil be of an es- 
pecially permeable character. If the culvert be the 
outlet of a side ditch, the outer wing wall and the floor 
of the culvert should be extended so as to reach beyond 
and under the ditch. These should be a continuation 



ROAD BRIDGES AND CULVERTS 137 

of the walls and floor of the culvert itself, so that the 
heaviest flow may not cause damage. At the outlet 
end the face and wing walls should be so constructed as 
to protect the embankment and assure the proper run- 
off for the water. 

Bridges are of such variety in type and must meet 
such varied requirements that only the general prin- 
ciples of their construction may be considered within 
the limits of this chapter. The materials are wood, 
steel, concrete, either plain or reinforced, and stone 
arches. 

The stone arch bridge has the sanction of history. 
There are stone arch bridges now in existence and 
carrying the traffic placed on them the history of which 
runs so far into antiquity as to be lost in its oblivion. 
For some unexplained reason modern engineers do not 
seem to favor stone arches. That they are practically 
indestructible, and that they are economical in those 
sections of country where stone is available, must be 
admitted. 

Wooden bridges have a temporary value only. While 
the first cost is less than that of those built of more dur- 
able materials, the cost of upkeep is excessive and under 
modern traffic conditions their life is likely to be short. 
In some instances, however, it occurs that timber is 
plenty and cheap, and that other materials are ex- 
pensive and difficult to get, so that a wooden bridge 



138 PRACTICAL ROAD BUILDING 

may well fill the gap and answer necessary purposes 
until a more permanent structure can be constructed. 
For short spans wooden bridges are usually built with 
joists extending from pier to pier or abutment, with a 
plank floor spiked to the joists. For longer spans there 
is a great variety of trusses to be selected from to secure 
that which may best fit the local condition. 

Iron and steel bridges are constructed in almost an 
infinity of styles and types. Until within a few years 
most of the important structures erected during the 
past half -century have been of iron or steel; iron in the 
earlier years, steel in the later. For a considerable 
period of time, from about 1880 to about 1900, a condi- 
tion prevailed which gave rise to numerous scandals in 
various parts of the country by reason of means used 
by steel bridge salesmen to secure several times the 
value of the bridge by imposing on either the ignorance 
or the cupidity of local road officials. It was not un- 
usual for a bridge which would cost less than $1000 to 
be sold for $4000, $5000, or even $6000, the representa- 
tives of the various companies deciding who should 
make the lowest bid, and each sharing in the profits. 
The system has been practically broken up. 

Nearly every bridge manufacturing company makes 
a number of standard styles and types of bridge which 
they can supply at reasonably short notice in different 
length of span at reasonable prices. Modification of 



ROAD BRIDGES AND CULVERTS 139 

these standard bridges may be secured at a small addi- 
tional expense. 

The plans of these standard bridges usually denote 
the guaranteed load-carrying capacity. This is an im- 
portant factor, as no highway bridge should be erected 
without a capacity for carrying a concentrated live load 
of at least 20 tons with a reasonable margin of safety 
beyond that weight. 

The custom has prevailed extensively, and still pre- 
vails to some extent, of accepting the advice of the con- 
tracting company's representatives as to the best type 
of bridge for a given locality; whether girder, pony 
truss or through truss, steel arch, etc. This is unwise. 
It must be remembered that the contracting company 
is actuated by other motives than are the highway offi- 
cials of the community ; and that even though perfectly 
honest, its recommendation might be influenced by con- 
ditions prevailing in its shops or in its business, rather 
than by the welfare of the community purchasing the 
bridge. 

The life of a modern steel bridge when properly cared 
for is estimated at from forty to fifty years. For this 
period of existence, however, the words "properly cared 
for" must be given their full significance. Thousands 
of steel bridges have gone to pieces in fifteen or twenty 
years, and sometimes less, because they were not given 
proper attention — properly cared for. 



140 PRACTICAL ROAD BUILDING 

Steel when not protected from moisture is subject to 
rapid deterioration by oxidization — rust. This is es- 
pecially true in places where the metal comes in con- 
tact, but not close enough to keep out the moisture, 
as at the joints in a bridge. Those parts exposed to the 
air, with alternate wetting and drying, suffer but little 
damage; but in the joints the rust is likely to eat into 
the heart of the metal and, without the damage being 
visible, produce a condition of dangerous weakness 
which is hard to detect until an "accident" happens. 

The care of a steel bridge includes keeping covered 
with special paint all joints and connections, so that 
the moisture shall be entirely excluded. The entire 
structure should be painted at least once a year; but 
the joints should be gone over at least twice a year, and 
oftener if the conditions of heat or cold have suggested 
breaks in the paint covering. If the bridge has any 
considerable area of riveting, the rivets should be gone 
over at least once a year with a hammer by some one 
who can tell a defective rivet by the sound when the 
hammer strikes it. By following these principles, and 
such others as the style of bridge may suggest, the 
greatest use possible may be secured from the structure. 

Concrete bridges have rapidly come into favor in 
recent years. The facts that there seems no limit to 
their life if properly constructed; that they can be made 
more attractive, so as to blend more harmoniously with 




141 



142 



PKACTICAL ROAD BUILDING 



surroundings; and that as a general rule the first cost is 
less than that of other comparable types, have given an 
impetus to their adoption throughout the entire country 
which may be considered remarkable. 

For long spans and large bridges the services of com- 
petent engineers are essential. Whether the bridge 













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jsP 




HPK"* 










I^L* 












-, . - .^sfC* - 




. -i :" - 




m 




, ; - r. ■ 



Fig. 13. — Illinois "short span" bridge. 

be of the beam, girder, or arch type, the very nature 
of concrete makes necessary a careful expert study of 
stresses and other conditions connected with the live 
and dead load that the bridge must carry. And to meet 
these requirements must be studied the character and 
quantity of the reinforcement and its proper placing; 
the particular mixture of concrete necessary to give the 



ROAD BRIDGES AND CULVERTS 



143 



proper strength under each individual condition; and a 
variety of other factors relating to the strength, bal- 
ance, and durability of the structure. Also to com- 
bine these structural elements with a design which shall 
be graceful and attractive and blend artistically with 
the surroundings; and a finish which shall be pleasing 




Fig. 14. — Concrete pile, cap and slab bridge over Bijou Creek, 

Colorado. 



to the eye. All these factors require engineering in- 
telligence of the first class. 

Forty-four of the forty-eight States of the Union 
have State Highway Departments with competent 
engineers. In nearly all of these states it is a part of 
the duties of the department to furnish to counties, 



144 



PEACTICAL KOAD BUILDING 



townships, or other subdivisions of the state informa- 
tion and advice, and in many states plans of bridges, 
and to supply expert inspectors to see that the work of 
contractors is properly performed. Such advice and 
assistance should be utilized to the fullest possible 
extent, especially in the case of long-span and large 
bridges, whether of steel or concrete. 




Fig. 15. — Concrete girder bridge, Colorado. 



Short span concrete bridges, by reason of their low 
first cost, their strength, and their presumably lasting 
qualities with low maintenance charge, have prac- 
tically revolutionized the practice in short span con- 
struction during the ten-year period from 1906 to 1916. 



ROAD BRIDGES AND CULVERTS 145 

While these are of almost infinite variety and plan, by 
far the greater number have been built from plans de- 
veloped by Mr.. A. N. Johnson, formerly State Highway 
Engineer of Illinois. In that state alone more than a 
thousand of these bridges have been built, and in many 
other states they have been extensively adopted. 








. **.' 



Fig. 16. — Type of "sectional" bridge. 

This plan provides for a combined reinforced con- 
crete girder and floor. Only two girders are employed, 
and these are above the floor, forming the side-rails of 
the bridge. For this reason the width of the roadway of 
the bridge is limited to about 18 or 20 feet. The ex- 
treme length should not exceed 40 or 50 feet, and the 
plan is most useful for spans of 30 feet and under. 

10 



146 PRACTICAL ROAD BUILDING 

The amount of reinforcement is adjusted to the 
length and width of the bridge at a fixed scale. The 
steel in girders is so arranged as to carry the ultimate 
weight of the bridge and load, and also to support the 
transverse reinforcement of the floor of the bridge. 
The floor, however, has reinforcing steel extending 
lengthwise as well as crosswise. 

The concrete used in these bridges is of a mixture of 
1 part cement, 2 J parts sand, and 4 parts of broken stone 
or gravel. The stone or gravel must not be less than 
f inch nor more than 1 inch in size. The compara- 
tively large amount of sand as compared to the stone is 
considered necessary because of the large area of sur- 
face exposed to the air, and also to insure solidity about 
the reinforcement. This proportion makes an excess 
of mortar which adds to the holding power of the con- 
crete on the reinforcing rods, and also makes a denser 
surface, which adds to the appearance of the structure, 
and at the same time makes it more impervious to 
weather conditions. 

These bridges are designed to carry a live load of 24 
tons distributed on two axles 10 feet apart, with 8 tons 
on the front and 16 tons on the rear axle. This live 
load is in addition to the "dead" load, or weight of the 
bridge structure. 

Plans and specifications for these bridges in lengths 
up to 40 feet may be obtained from the Illinois Highway 



ROAD BRIDGES AND CULVERTS 147 

Department, Springfield, 111. Most of the details 
may be found in the various reports of the department 
together with costs of construction of various bridges. 
These latter vary so widely, however, owing to vari- 
ance in conditions that they hardly furnish a guide. 

On most bridges, even on wooden structures, the 
tendency in recent years has been to use concrete floors. 
These are easily laid, and especially if reinforcement is 
used, most experts hold that the added dead weight on 
the bridge structure is more than counteracted by the 
rigidity which the concrete floor gives, with the re- 
sulting reduction of vibration. Also, a concrete floor 
lasts many times as long as a plank floor, and the cost 
of its upkeep is negligible, making it much cheaper in 
the long run. 

It is usually considered that a good concrete foreman 
is capable of building the short-span concrete bridges 
above described, and of placing concrete floors on exist- 
ing structures without further engineering directions 
than are found in the plans and specifications. Inspec- 
tion by a state highway official, if available, is, how- 
ever, always wise. 

Foundations for highway bridges have in recent 
years followed closely the principles for railway bridges. 
It has been found in many instances that a foundation 
that would carry the weight of a bridge and load might 
be easily undermined by flood water in case of a freshet. 



148 PRACTICAL ROAD BUILDING 

It is, therefore, considered the best practice, if bed-rock 
cannot readily be reached, to drive long piles to a prac- 
tically solid bearing, and place the masonry or concrete 
abutments and piers on the top of the piles. Wooden 
piles should be cut off some distance below the low water 
level, and generally below the bed of the stream. Con- 
crete piles are often used, formed by driving down a 
steel core with a sheet iron shell, then withdrawing 
the core and filling the shell with concrete. In this 
form of pile it is possible to have the bottom of the 
shell opened and a quantity of concrete forced out into 
the surrounding earth if it is soft enough, making a 
broader foundation, the pile taking the shape of an 
inverted mushroom. Other styles of piles are made, 
with or without reinforcement, and either driven to 
place by specially prepared pile-drivers, or sunk into 
place — in sandy earth — by the action of a small jet of 
water at high pressure at the point of the pile. 

Steel caissons with a timber framework at the bottom 
and concrete at the top have been much used. These 
are sunk into mud bottoms as far as possible, and the 
piers and abutments built on them when they have 
reached an apparently secure resting place. There is 
often danger that the resting place is not secure. 
Caissons are sometimes sunk to bed rock or to a solid 
foundation, the space within the caisson excavated dur- 
ing the sinking operation, and then the caisson filled 



ROAD BRIDGES AND CULVERTS 149 

with stone, concrete, or such other material as will 
make an absolutely solid base. The individual treat- 
ment in each case depends on the soil and other con- 
ditions encountered. 

Piers and abutments should always be parallel with 
the flow of the water. If the bridge must cross the 
stream diagonally, the skew must be in the bridge rather 
than in the piers and abutments. Girder bridges built 
on a skew are readily adjusted; arch bridges on skew 
present technical features in stress distribution which 
require accurate engineering study. 

The basic factor in securing a satisfactory pier and 
abutment foundation for a bridge is to get to a depth or 
to a condition of solid earth or rock, so that they will 
neither settle nor wash out. 

Floorings on bridges may be made of any desired 
material, usually governed by the cost. Concrete 
bridges and many steel bridges have concrete floors. 
Sheet asphalt, asphaltic concrete, brick, wood block 
(creosoted), and a variety of other floors are in general 
use. A study of which is best adapted to the traffic 
and, therefore, most economical, under local conditions, 
is necessary for the determination as to which is most 
available. 



CHAPTER VIII 



ROAD TRAFFIC 



Before beginning the construction of a new road or 
the reconstruction of an old one a careful study should 
be made as to the amount and character of the traffic 
which the road will have to carry after its improvement. 
The importance of this study cannot be overempha- 
sized, as there is always a great increase in traffic after 
a road has been improved. Travel will invariably go a 
considerable distance from its most direct route if by 
so doing it can reach a good road. 

Previous to the general use of motor cars the changes 
in courses of travel could be readily estimated. Since 
the tremendous development of this method of trans- 
portation the subject is one which calls for the best and 
most careful consideration by road officials. The road 
which is sufficiently well built so that it will carry light 
and heavy horse-drawn traffic may go to pieces directly 
under the motor truck or the motor omnibus. It is 
worthy of note that with the improvement of the roads 
motor-bus and motor-freight lines are springing up by 
hundreds, furnishing regular passenger and freight 
schedules to communities either off the line of a rail- 

150 



ROAD TRAFFIC 151 

road, or where the local railway service is unsatisfac- 
tory. 

The traffic census, that is, counting the vehicles and 
animals passing over the roads, was first practised in 
France about 1840, though the custom had prevailed in 
separated localities previous to that time. Since then 
there has been a regular census of traffic taken over all 
the roads in that country at intervals ranging from six 
to ten years. Since the advent of the automobile the 
traffic on certain roads where the travel is heaviest has 
been taken at more frequent intervals in order to as- 
certain a basis for determining the proper kind of re- 
pairs necessary to preserve the roads. 

In England for many years a traffic census has been 
carried on, by County Councils on various roads when 
there seemed to be a need for it. In 1912 control of 
the traffic census was taken over by the Road Board, 
and is now conducted regularly and simultaneously 
throughout that country. The actual work of making 
the count is still in the hands of the County Councils, 
but under the direction of the Road Board, thus secur- 
ing uniformity of method and dates of counting, and 
of classification of the units or items of traffic. 

In this country only occasional counts were made of 
road traffic in various localities until 1909. During 
that year the Massachusetts Highway Department 
organized a traffic census covering a large portion of 



152 PRACTICAL ROAD BUILDING 

the main roads of that state, and has kept it up at three- 
year intervals. The same year the Illinois Highway 
Department caused a census to be taken of the traffic 
at a large number of important points, at many of 
which the traffic has been again counted at such inter- 
vals as the conditions seemed to warrant. 

As an illustration of the remarkable change which 
sometimes occurs in the volume of traffic over a road, 
the chairman of the Massachusetts Highway Commis- 
sion, in an address at the Pan-American Road Congress 
(Oakland, California, 1915), mentioned one of the 
roads of his state. The road mentioned was 26 miles 
long. In 1909 the traffic census showed it carrying 37 
automobiles a day, as well as a fair amount of horse- 
drawn traffic. In 1912 the number of automobiles 
daily was 250, and in 1915 the count showed a little 
more than 1000 automobiles a day, the horse traffic re- 
maining about the same or a trifle less than it was in 
1909. The especial point of the remark was that the 
road, having a gravel surface, would carry the traffic 
economically up to and past the 250 motor cars per 
day, but when the number reached anywhere near 
1000 (probably near 500) the cost of keeping the gravel 
road in condition was so great that economy demanded 
that the road be rebuilt with a stronger and more dur- 
able surface. 

It is, of course, impossible to form an accurate esti- 



ROAD TRAFFIC 153 

mate at all times. Sometimes new conditions will arise 
by the construction of bridges in new locations, or by 
the organization of through routes of travel, or by the 
development of new industries made possible by the 
improvement of the roads. But a fair judgment can 
be made in most instances by taking a census of the 
present traffic and using it as a basis from which to 
figure the probable accumulations from parallel routes 
and from additional accessible communities after the 
road shall have been improved. 

In taking a census of the traffic two methods are in 
use, each having its advocates: One method is to set 
apart a week in the spring and a week in the fall, and 
have the count made during seven full days at each 
period, the hours being usually from 7 a. m. to 7 p. m., 
though the hours may be changed to suit the particular 
travel habits in various localities. The other method 
is to use seven weeks in making the count, taking Sun- 
day of one week, Monday of the next week, Tuesday 
of the next, and so on until a complete week has been 
covered. Advocates of this latter method claim that it 
gives a fairer average by distributing the count over a 
greater period of time, while those favoring the first 
method consider that it is possible to secure a better 
organization for the work if it is done on consecutive 
days. 

In taking the traffic census arrangements are usually 



154 PRACTICAL ROAD BUILDING 

made with some resident of the immediate vicinity of 
each point decided on. In many instances, especially 
in those months when schools are not in session, stu- 
dents are employed for the purpose. Many persons, 
recognizing the public nature of the work of making the 
count, volunteer their services gratuitously; others will 
accept but a small compensation. In any case it is 
necessary that the sense of responsibility of the person 
making the count be sufficient to insure thorough and 
reliable work and results. 

The points fixed upon for counting the traffic are 
usually a little out of the city or village — far enough to 
avoid the traffic which belongs in the city and yet near 
enough to include all the outside traffic to or from the 
city over that particular road. When the points have 
been selected and the census takers duly appointed, 
each census taker should be supplied with printed in- 
structions and blanks which should be prepared in such 
simple form as to make mistakes practically impossible. 

Different states and different countries have each 
their special classifications of vehicles. Some are very 
elaborate, with fifteen or twenty separate items. For all 
practical purposes, however, the following division of 
the traffic seems sufficient: 

Automobiles: 
Runabouts, 
Touring cars, 
Motor trucks. 



ROAD TRAFFIC 155 



Horse-drawn vehicles: 

1 -horse light, 

1 -horse heavy, 

2 or more horses light, 

2 or more horses heavj'. 
Special: 

Traction engines, 

Motor omnibus, 

Freight motor with trailers. 



With the list printed on the left of the sheet and wide 
lines left for marking a "/" m the proper place at the 
passage of each vehicle the work is easily performed. 
On many country roads the counting has been done by 
housewives without materially interfering with their 
household duties. It was only necessary that they keep 
in sight of the road. At the close of each day and at 
the end of the period the traffic can be footed up and 
the proper comparisons made. 

As to what kind of a road to build and how to build 
it, after the actual traffic has been counted and the 
future traffic estimated as carefully as possible, there 
has been much experimenting, and many hasty con- 
clusions formed. There are some cases, however, where 
experiments have been carried on over a series of years 
and the results carefully recorded and made use of. 
Of these, the reports of the Massachusetts Highway 
Department furnish the most comprehensive and re- 
liable record reported, both on account of the continu- 
ance of the experiments through a series of years and 



156 PRACTICAL ROAD BUILDING 

of the practical use made of them under the constantly 
changing conditions. It is possible that other equally 
valuable information may have been secured, but not 
reported in form to make it available to the public 
generally. 

The Massachusetts Department says in its report: 

A good gravel road will wear reasonably well and be 
economical with a traffic of 50 to 75 light teams (1 or 
2 horses), 25 to 30 loaded 1 -horse teams, 10 to 12 loaded 
2-horse teams, and 100 to 150 automobiles. If the num- 
ber of automobiles averages above 150 per day the road 
should be oiled. 

An oiled gravel road, with good oil applied either hot 
or cold, ^ gallon to the square yard (cold oil must be 
used yearly), will carry a traffic of 75 to 100 light teams, 
30 to 50 loaded 1-horse teams, 20 loaded 2-horse teams, 
and 500 to 700 automobiles of all classes. 

A water-bound macadam road will stand a traffic of 
175 to 200 light teams, 175 to 200 heavy 1-horse teams, 
60 to 80 and perhaps more heavy 2-horse teams, but 
not to exceed 75 automobiles, especially if they move at 
fairly high speed. A dust layer will be serviceable when 
the automobiles range from 50 to 100. With a good dust 
layer kept well applied the road will stand 300 to 500 
automobiles a day in addition to the team traffic, al- 
though the stone in the macadam will wear. 

Water-bound macadam with a hot oil blanket coat 
will be economical with 150 to 200 light teams (1 or 2 
horses), 75 to 100 loaded 1-horse teams, 25 to 30 loaded 
2-horse teams, and automobiles up to 1400 in number. 
The large number of pneumatic tires has been found to 
iron out the depressions caused by steel tires in the 
road and keep it rolled down smooth. The road will 
not be injured by 50 or perhaps more motor trucks, but 
it will crumble and perhaps fail with more than 100 
loaded 1-horse and 50 or more loaded 2-horse teams, 
such as loaded farm wagons, ice wagons, wood wagons, 
etc., especially on narrow tires. 



KOAD TRAFFIC 157 

(All the figures given in the statement represent aver- 
age daily traffic, and in most cases seem to be based on 
conclusions drawn from examples of maintenance of old 
rather than of newly built roads. This seems especially 
probable in view of the fact that the Massachusetts 
Highway Department no longer builds water-bound 
macadam surfaces on its main roads, but employs more 
durable surfaces exclusively.) 

In some states laws have been enacted limiting the 
loads to be carried to 800 pounds per inch of width of 
tire. Narrow steel tires on heavily loaded wagons or 
trucks are considered the most destructive agency to 
which the roads are subject. Solid rubber tires on 
motor trucks are usually constructed of much greater 
width than would be required by such a law, and the 
rubber does not have the same destructive force as steel 
tires; while a pneumatic tire of whatever size flattens 
out under a load, and presents an enlarged surface which 
is beneficial to the road surface rather than otherwise. 
But steel tires under heavy loads and with sharp 
corners cut into the road surface, leaving depressions 
where water accumulates; then more traffic churns the 
water, and soon there is a mud-hole, and a rapid soften- 
ing and displacement of the material forming the road 
surface. 

In some instances computations have been made to 
determine the weight of traffic per foot of the width of 



158 PRACTICAL ROAD BUILDING 

the road. This practice is necessary for a complete 
knowledge of the stresses on city streets, and perhaps 
on a few broad boulevards where the entire road surface 
is in constant use; but on country roads, where the 
vehicles invariably follow each other in a single or a 
double track, the knowledge gained will be useless and 
confusing. 

In taking a traffic census special attention should be 
given to the extra heavy vehicles, such as traction 
engines, road rollers, etc., and some of the very heavy 
motor freight trucks which are rapidly coming into use, 
Usually these vehicles do not damage the road surface 
on account of the width of the tires, having a tendency 
to compact and improve the surface; but except in the 
case of very well built roads their weight is liable to 
fracture the foundations. There are many of the older 
bridges on the roads throughout the country which will 
not stand under these heavy weights. Until about ten 
years ago most highway bridges were built to sustain 
not more than 4 to 8 tons. Such bridges, until re- 
placed by stronger ones built with reference to the 
weight of modern vehicles, must either be braced or in 
some way given additional support; or else the heavy 
vehicles must be kept off them. Slats or other projec- 
tions should not be permitted on traction engine wheels 
on any hard surfaced road. 

Traffic regulations are usually fixed by law, the laws 



ROAD TRAFFIC 159 

varying in the different states. Speed limitations, un- 
less within liberal limits and liberally construed, have 
generally been found vexatious and unprofitable. The 
most satisfactory method of controlling the speed ques- 
tion has been found to consist in demanding and en- 
forcing a reasonable speed, according to conditions. 

A speed which might be reasonable at one point on a 
road might be entirely unreasonable at another point; 
or which would be reasonable at one hour of the day, 
unreasonable at another hour. On a wide straight- 
away road, with no road-crossings, and no obscurities 
for other traffic, and with pedestrians absent, almost 
any speed at which a motorist might wish to travel 
could be considered reasonable. If there were fre- 
quent cross-roads, or much travel, or any other factor 
which would make speed dangerous to people or prop- 
erty on the road, then the speed should be reduced 
until all danger should be eliminated, even to the speed 
of a man walking. Responsible motorists are the first 
to condemn reckless driving, and punishment of offend- 
ers should be based on recklessness in driving rather 
than on miles per hour. 

In states where the licensing of automobile drivers is 
in the hands of the State Highway Department the 
question of safe driving is much more easily controlled 
than where the roads and licenses are under separate 
control. Reports of violations, accidents, etc., all re- 



160 PRACTICAL ROAD BUILDING 

ported to the common department head, gives a more 
comprehensive knowledge of those individuals who 
habitually violate the rights of others, and permits 
licenses to be cancelled when necessary without very 
much "red tape." 

One broad principle in connection with road traffic 
must always be borne in mind: No single individual 
has the right, legally or morally, to either damage the 
road, which belongs to all, or to so use it as to endanger 
the life, property, or happiness of another. 



CHAPTER IX 



ROAD FINANCE 



There are two basic factors in road finance : getting 
the money, and spending it to the best advantage. 

Getting the money involves the questions of valua- 
tion, taxation, bonds, either sinking-fund or serial, and 
outside aid or contributions. Spending the money takes 
into consideration the advantages or disadvantages of 
location regarding materials; freight rates; the most 
economical kind of road for the traffic; and the local 
laws respecting bids and bidding. 

Getting the Money 

In some well-settled and wealthy communities where 
land values are high direct taxation for road building 
is considered wise. But the localities where such taxes 
can be levied without being burdensome comprises a 
very small percentage of the country. Almost every- 
where, if good roads are to be built, the cost must be 
distributed over a series of years. The length of time 
over which the cost must be spread depends on the 
sentiment of the community and the local laws regulat- 
ing bond issues. In issuing bonds consideration must 

11 161 



162 PRACTICAL ROAD BUILDING 

be given to the fact that the people have the use of the 
improved road while paying for it. 

In some states there is a provision for five- and ten- 
year certificates which those directly involved may take 
advantage of. This, however, is usually confined to 
the few localities where the cost of construction, or 
some part of it, is taxed against the adjacent property. 
Taxing the adjacent property to build roads for all the 
people is recognized in modern times as a wrong prin- 
ciple, and has been discontinued in most of the states. 

Generally, bonds are of three classes: Sinking fund 
bonds, serial bonds, and annuity bonds. 

Sinking-fund bonds are those which run for a stated 
term of years, and which require that a certain percent- 
age or a certain amount be set aside every year as a sink- 
ing fund for the payment of the principal at the maturity 
of the bonds. There is often misapprehension or faulty 
figuring on the amount to be thus set aside. The sink- 
ing fund should be so invested from time to time as to 
draw compound interest at the best rate that can be 
obtained. In many counties the county boards invest 
the money of the sinking fund in other local securities, 
thus getting the same rate of interest on the sinking 
fund money as is being paid on the bonds. One county 
which came under the author's observation was able 
to take a full issue of $100,000 of road bonds with the 
money in the sinking funds of other county securities. 



ROAD FINANCE 163 

These funds had been drawing 3 J or 4 per cent, interest. 
By investing in the issue of road bonds they drew 6 per 
cent., and only the interest was left to be invested an- 
nually or semi-annually until the maturity of the bonds. 

Compound interest tables will show what amount 
invested annually at compound interest will reach a 
given amount in a given period. For instance, 1 per 
cent, of the face value of a bond invested and com- 
pounded annually at 3 \ per cent, interest will produce 
enough money to pay the bond in a little less than forty- 
eight years. This amount is frequently used, and col- 
lected at the same time as the interest, when fifty-year 
bonds are issued. With a higher rate of interest, such 
as would be obtained by investing in the same or other 
securities, the term would be shortened or the annual 
sinking fund investment reduced. 

Compound interest tables, which are easily procured, 
will show the amount necessary to be deposited in a 
sinking fund at any ordinary rate of interest for any 
general term of years. Nearly all banks have these 
tables, and they are in the rate book of nearly every life 
insurance company. They can be purchased for a small 
amount at almost any news-stand. The proper table is 
easily applied to any condition of term of bonds and 
rate of interest, so that every one interested may easily 
secure complete information on the subject. The 
tables are too long for reproduction here. 



164 PRACTICAL ROAD BUILDING 

Serial bonds are in much favor in some localities. 
These bonds are numbered, and are usually made in 
uniform amounts. An issue of $100,000 might be made 
in 100 bonds of $1000 each or, if intended for subscrip- 
tion by the people of the community, might be made in 
denominations of $100 each, which would cause the 
numbers to run to 1000. This applies to all cases where 
it is desired to give an opportunity to local investors, 
both of large and small means, to subscribe to the 
bonds. 

With serial bonds, in addition to provision for paying 
the interest, the money for the principal instead of 
going into a sinking fund is used to pay the bonds ac- 
cording to their serial numbers. As an instance, 
$100,000 of bonds might be made payable at the rate 
of $4000 each year for twenty-five years, or $5000 each 
year for twenty years ; or a period may be chosen which, 
by paying $20,000 or $25,000 at each time of payment, 
will reach the final payment in twenty-five or twenty 
years. 

Take $100,000, to be finally paid in twenty-five 
years. The annual interest at 5 per cent, will amount 
during the first five years to $5000 per year. At the 
end of the first five years the first twenty of the $1000 
bonds are to be paid and provision must be made for 
$20,000 required for this payment. During the next 
five years the interest is reduced to $4000 a year, or 5 



ROAD FINANCE 165 

per cent, on $80,000. At ten years the next twenty 
bonds are paid, reducing the interest to $3000 a year, 
and so on, until after the twentieth year the interest 
amounts to but $1000 a year, and at twenty-five years 
ceases entirely, when the last twenty bonds are paid, 
finally cancelling the debt. 

In former years trust companies and large bond- 
purchasing concerns did not look with favor on serial 
bonds, preferring the long-time sinking-fund bonds 
which gave them less trouble in re-investing the funds 
under their control. In some instances there may have 
been a fear of reducing the amount of sinking-fund 
money which might be placed in their hands on deposit 
at low interest rates. In recent years, however, these 
financial institutions have taken more kindly to the 
serial bonds, so that at the present time (1917) they 
command a price in the larger financial markets fully 
equal to those of uniform term. 

Annuity bonds, while of long and favorable use in 
private business and real estate transactions, are com- 
paratively new in their application to public securities. 
The plan is to so figure the interest, principal, and term 
into a system that all the annual or semi-annual pay- 
ments shall be practically the same, so that the debt 
will be paid in a given number of equal installments. 
To illustrate the working out of the annuity bond sys- 
tem the accompanying table has been rearranged from 



166 PRACTICAL ROAD BUILDING 

a scientific document published by the United States 
Department of Agriculture. The table is based on a 
loan of $100,000 payable in three years, in six semi- 
annual payments, the interest being at the rate of 5 
per cent. A simple computation in partial payments 
will adapt the plan to any other amount for any period 
of time and at any desired rate of interest. The table 
follows : 

Principal Interest at Principal paid at Semi-annual 

Time. outstanding, each payment, each payment. payment. 

6 months.... $100,000.00 $2500.00 $15,655.00 $18,155.00 

1 year 84,345.00 2108.63 16,046.37 18,155.00 

H years 68,298.63 1707.47 16,447.53 18,155.00 

2 years 51,851.10 1296.28 16,858.72 18,155.00 

2^ years 34,992.38 874.81 17,280.19 18,155.00 

3 years 17,712.19 442.81 17,712.19 18,155.00 

Totals $8930.00 $100,000.00 $108,930.00 

Examination of this table shows that the reduction of 
the principal amount increases as the interest payments 
become less, the first payment on the principal being 
$15,655, while the last one is $17,712.19. 

Some communities seem to favor the annuity bond 
plan, as it gives them an exact idea of what they must 
pay each year, and because it is the same amount at 
each payment period; while in serial bonds the interest 
payments are heavier at the beginning, and become 
smaller as the bonds are paid off; and with sinking- 
fund bonds much depends on the rate of interest that 
can be secured for the sinking-fund money. 



ROAD FINANCE 167 

Misapprehension of the expense of bonds and the 
amount of value to be derived from their issue exists in 
some localities where bonds for roads have been de- 
feated. A simple form for determining the cost to each 
taxpayer is to get as accurately as possible the number 
of acres which will be taxed to pay the principal and 
interest on the bonds annually, and figure what will 
be the average cost per acre per year. The result will 
surprise many who object to bonds. Another plan is 
to take the amount which must be paid annually on the 
bonds, principal and interest, and divide it among the 
total assessed valuation of the district involved so as to 
get the rate of additional taxation. This rate extended 
in any individual case will show the amount of extra 
taxation which the bonds will involve. In most cases 
the amount will be so small as to silence objection to 
the bond issue. 

On some roads in some sections of the country pri- 
vate individuals, corporations, automobile clubs, and 
other corporations are found willing to contribute cer- 
tain amounts toward the cost of a road, either as a 
matter of creditable public spirit, or for furthering an 
improvement which may benefit them, or for both rea- 
sons. The roads built with the aid of such donations 
are constantly increasing in number, and indicate a 
growing intelligence on the subject of the value of im- 
proved roads to a community. 



168 PRACTICAL . ROAD BUILDING 

Statistical experts have figured that the building of a 
good road leading to a market town or business center 
increases the value of the farm land accommodated by 
the road from 15 to 50 per cent., and cases are not rare 
where land has even doubled in value within a year after 
a road was built. This increase is due principally to 
the decreased cost of hauling crops and supplies over 
the road, and the larger number of crops that can be 
profitably grown by reason of cheap hauling at all 
seasons of the year. 

Spending the Money 

The type of road to be economically built in any com- 
munity should be determined as far as possible by the 
availability of materials. In almost every section there 
is some material which, either by itself or in combina- 
tion with some other material which is not too expen- 
sive, will make a fair road at a reasonably low first cost. 
If the location be one where a high-class road is neces- 
sary and there is no suitable local material, the added 
cost of shipping in outside materials must be considered 
as part of the road investment. 

The points on which to figure are: The relation of 
the first cost and the cost of upkeep for a series of years 
of the road built cheaply and of inferior materials, as 
compared with the first cost and the cost of upkeep of 
the more expensive road. 



ROAD FINANCE 169 

A good road, made of first-class materials, should 
require but a small outlay for repairs for a number of 
years; while the road built of inferior materials will re- 
quire repairs more or less constantly, according to the 
quality of the material and the character of the traffic. 
In this connection it is held that when the annual cost 
of keeping an inexpensive road in repair amounts to 
enough to pay the interest on the money necessary to 
build a good road, it is economy to build the good 
one. The same rule will apply to all classes of roads, 
wherever located. The particular advantage is that 
without additional cost a good road may be had in- 
stead of one which is in a condition where constant re- 
pair is necessary. 

The laws of various states vary greatly as regards con- 
struction. In many states all construction must be 
let by contract; in some states the lowest bid must be 
accepted ; in some states officials can build the roads on 
force account, and in some convicts may be employed. 

Where construction is done by contract the specifica- 
tions should be carefully drawn before bids are invited, 
so that no materials or workmanship may be employed 
of a lower grade than that intended. In some materials 
which have names which indicate their general char- 
acter there is a vast difference in excellence. The 
word "asphalt," for instance, covers all materials with 
an asphaltic base, whether mined from the asphalt 



170 PRACTICAL ROAD BUILDING 

lakes of South America, or those which are the resid- 
uum of petroleums from the oil wells of the United 
States and of Mexico. Care should be taken, after 
investigation, to specify as accurately as possible the 
exact material required whenever it is possible to do so. 

There are three definite kinds of specifications, either 
of which may be employed where the law permits: 
One is the "open" specification, sometimes called a 
blanket specification, the limits of which are so broad 
as to admit all classes of materials and types of road. 
This gives an opportunity for competition in materials 
as well as price, and gives the road authorities an oppor- 
tunity to study the respective advantages of the differ- 
ent materials and roads at the prices named. But this 
"open" specification may not be used when the law 
requires the acceptance of the lowest bid, as that would 
necessarily mean the poorest road, of the cheapest 
material. If the road officials have undisputed author- 
ity in the matter of accepting what seems to them the 
best proposition, the "open" specification has many 
advantages. 

The ''closed" specification enables the road officials 
to get exactly the materials they want, as the specifica- 
tions are drawn with reference to that particular 
material. Objectors to the closed specification claim 
that this form limits competition and tends to higher 
prices, by reason of keeping out other competitive 



ROAD FINANCE 171 

materials. While this may be a fact in isolated in- 
stances, it is a fact that nearly all large manufacturers 
of road materials will sell to all contractors at the same 
price; so that competition must be between the con- 
tractors for the work and other factors entering into 
the construction. As before stated, in the opinion of 
the author, especially as to such materials as brick or 
asphalt, the specifications should state definitely the 
particular material desired. 

"Alternate" specifications, which describe two or 
more types of roads or classes of material, are sometimes 
used. This "alternate" specification has the effect of 
enabling the officials to receive bids by which they can 
balance against each other the relative advantages and 
price of the different types of road. It may also be 
drawn so as to describe different classes or grades of 
the same material, and thus the officials may have a 
chance to decide what particular material at the price 
bid will be of the greatest advantage to the community. 
The "alternate" specification has the effect of a series 
of "closed" specifications competing against each other. 

Where work on road construction is done under the 
supervision of local officials on force account the most 
careful records of all costs should be kept and properly 
classified, not only that the public may be kept fully 
posted, but that other or subsequent officials may have 
the benefit of the information they contain. 



172 PRACTICAL ROAD BUILDING 

Nearly all the states of the Union grant state aid in 
road building in some form, either cash, or convict 
labor, or engineering services, and sometimes in two or 
more of these forms. Such aid should be taken ad- 
vantage of to the fullest extent, and all local officials and 
others interested should keep in close touch with the 
Highway Department of their state. 

The Federal Aid Good Roads Act, which became a 
law in July, 1916, appropriates $5,000,000 for the con- 
struction of roads during the year ending June 30, 
1917, $10,000,000 for 1918, $15,000,000 for 1919, 
$20,000,000 for 1920, and $25,000,000 for year ending 
June 30, 1921. It also appropriates $1,000,000 per year 
for ten years for constructing roads in national parks. 

The money thus appropriated is divided among the 
states in three ways : One-third according to the ratio 
of population; one- third according to the ratio of area, 
and one-third according to the ratio of mileage of rural 
mail routes and post-roads. In establishing the ratios, 
the population, area, and mileage of post-roads are 
each figured in relation to the totals of those factors in 
the United States. 

The funds thus appropriated are paid by the Federal 
Treasury to any state as payment of one-half the cost 
of construction of any road agreed upon by the Highway 
Department of the state and the Secretary of Agricul- 
ture of the United States, and after the state has pro- 



ROAD FINANCE 173 

vided for the other half of the cost. The roads built 
with the aid of Federal funds must be of substantial 
character, and be inspected and approved by Federal 
engineers. The states must agree to maintain the 
roads so built. 

The office of Public Roads and Rural Engineering, 
Washington, D. C, has the rank of a bureau in the 
Department of Agriculture. It furnishes the services 
of road engineers on the request of local highway offi- 
cials, and publishes many bulletins and other docu- 
ments on road subjects which can be procured by those 
who are interested. Most of these documents are sent 
free on request; others are subject to a slight charge. 



PART II 



CHAPTER X 

EARTH ROADS 

Earth roads we have always with us, and are likely 
to have in the future, indefinitely. Of the approxi- 
mately 2,200,000 miles of roads in the United States, 
about 2,000,000 miles are earth roads. Some of these 
have been improved by draining, shaping, and grading, 
but by far the greatest part of the mileage still consists 
of the practically unimproved earth road. 

The reason for this condition lies in the fact that from 
80 to 85 per cent, of the road traffic of the country is 
carried on from 15 to 20 per cent, of the roads. The 
main roads, on which the travel comes together from 
every direction in its movement toward the city, or 
village, or shipping center, requires a better surface 
than any of those which lead to them. These main 
roads are dealt with in other chapters. 

The system by which the relative travel over various 
roads has been accurately determined was worked out 
some years ago by Mr. A. N. Johnson, then State High- 

175 



176 PRACTICAL ROAD BUILDING 

way Engineer of Illinois. He took as a basis an aver- 
age township, 6 miles square, with a village in its center. 
At the village are the railroad station, the post office, the 
stores where hardware, dry goods, groceries, and other 
supplies are purchased, repair shops of various kinds, 
the churches, the newspaper, the graded school with 
high school department, and in some states the town- 
ship school, which has taken the place of the former 
district school. The village is also usually the center 
of social activity for the surrounding country. 

With a road on each section line, there would be 36 
miles of north and south roads, and 36 miles of east and 
west roads, 72 miles in all. The center road of the town- 
ship in each direction, crossing at the village in the 
center, should be termed the main roads. These 
would be 6 miles long each or 12 miles in all. This 
amounts to 16f per cent, of all the roads, which must 
be classed as main roads, and improved accordingly. 
The other 83 J per cent, of the roads, which carry the 
travel to the main roads, does not require the expen- 
sive treatment which must be given the main roads. 

Taking each quarter section as a farm, and each 
farmer making two trips to town each week, it is easily 
shown that every person in the township uses the main 
road for at least a part of his trip. The most remote 
resident travels 2J miles over the side road and 3 miles 
over the main road in reaching the village. Forty- 



EARTH ROADS 177 

four reside on the main road ; thirty-six are a mile from 
the main road; twenty are 1| miles away, and twelve 
are 2 miles, making, with the four that must travel 
2| miles to reach the main highway, the 144 quarter 
sections into which the township is divided. Each of 
these residents takes the shortest course to the main 
road, thus aggregating upon it fully 85 per cent, of all 
the travel. 

While each citizen is entitled to a road which will 
carry his traffic, the expenditure of the same amount of 
money, for similar improvement, on the road that is 
used by ten loaded teams per day and on that which 
carries one hundred such loads would be wasteful. 
Either more money would be spent on the side roads 
than is necessary or the improvement to the main road 
would be of such poor quality that the road would soon 
go to pieces. 

The figures, as given above, are more readily worked 
out with the township under what is known as the Con- 
gressional Survey. In the original thirteen states of 
the Union, where most of the surveys were more prim- 
itive and irregular, careful observation has shown that 
the relative percentages are practically the same. 

The width of the earth road must depend on the 
present and prospective travel, but should range from 
20 to 30 feet between centers of ditches. The right of 
way usually runs from 40 to 66 feet. The surface of 

12 



178 PRACTICAL ROAD BUILDING 

the roadway should be curved or rounded into a crown 
with the highest point in the center of the road where 
the road is straight; on a curve the slope should be in- 
ward from the outside, and on a side hill the highest 
point in the crown should be two-thirds or three-quar- 
ters of the way toward the outside edge. 

The height of the crown of the road should be meas- 
ured from the bottom of the side ditches, and must 
depend on the character of the earth of which the road 
is made. It should be sufficient so that rain or other 
surface water will readily run off into the ditches, but 
without damage or wash to the road. It must not be 
too high, or vehicles will keep to the top, and by follow- 
ing in each other's tracks form ruts; and the water, 
getting into the ruts, and being churned by other 
vehicles, will soon cause the formation of mud-holes 
and a gradual disintegration of the road. Nor shall 
the road be too flat unless the soil be sandy; because 
a flat road soon becomes a depressed one, and water 
will stand on it, and water will destroy the usefulness of 
any road sooner or later. 

After the grade of an earth road has been decided on 
(see Chapter III), the alignment of the traveled portion 
to be improved becomes important. It is not unusual 
to find country roads, extending for miles between 
straight line fences, winding from one side to the 
other of the right of way, instead of maintaining a 



EARTH ROADS 179 

straight line in the center. This irregularity should be 
corrected when the road is improved. The ordinary 
way of doing this is by establishing a center line of the 
road midway between the two fences, setting stakes at 
frequent intervals, and sighting along the stakes to see 
that they make a perfectly straight line. Then 
measurements may be taken from the center of the 
road to the center of the ditch on each side, and other 
stakes driven beyond the ditch to indicate the slope 
of the outer side of the ditch. This slope may be 1 foot 
back to each foot of depth, or lj feet or even 2 feet, 
according to the soil. In a firm soil a 1 : 1 slope is 
sufficient; while in a soil which will wash easily a 2 : 1 
slope is none too much. The principle involved is that 
all care must be taken to keep the ditch from filling up 
or becoming clogged. 

In improving the earth road much depends on the 
location. If the grade requires a cut and a fill in close 
proximity, ordinary farm ploughs and drag scrapers 
can be used economically. These carry the dirt from 
the cut to the fill with one movement. If the distance 
be more than 50 to 100 yards, wheel scrapers are more 
economical, as they carry two or three times as much 
earth with approximately the same horsepower and 
labor. Wheel scrapers are rarely economical, however, 
in stony or rocky ground. 

Where the ground is practically level the ordinary 



180 PRACTICAL ROAD BUILDING 

road grader can be used to excellent advantage. It is 
better not to run the blade of the grader too deep at any 
one cutting, as that has a tendency to throw the earth 
toward the center of the road in lumps or chunks. 
Rather, the grader should take comparatively thin 
depths of earth and spread it thinly in courses over the 
roadway. This method secures a more even distribu- 
tion and density of the earth placed on the roadway, and 
makes a smoother and better road when it is packed 
down either with a road roller or by the travel. 

If the ground be low or swampy so that the road has 
to be built up, an elevating grader will be found econom- 
ical and serviceable. These machines not only move 
earth at a reasonable cost, but they deposit it with 
such regularity of position that a saving is effected in 
the subsequent work. 

Whatever implements may be used in building an 
earth road, it is essential that no vegetation be left on 
or in the roadway. All sods, grass, weeds, bushes, 
leaves, and every other growth should be placed out- 
side the ditches, so that by no possibility may they get 
to the roadway. Decaying vegetation attracts moist- 
ure; and moisture distributed unevenly in or under the 
surface of a road soon fills the roadway with holes and 
irregular depressions, which, if not repaired promptly, 
soon makes a bad road out of what should have been a 
good one. 



EARTH ROADS 181 

In some cases it may be found that the road can be 
brought to the required shape and the earth evenly 
distributed by the use of the grading machine. Gen- 
erally, however, much may be gained by giving it a 
thorough dragging with a square tooth farm harrow. 
This dragging, if done thoroughly, brings about a uni- 
formity of density that is necessary in securing a smooth 
and even surface. Where the top soil is sand or gravel, 
and the grader brings up earth from the ditches which 
has an admixture of clay, a disc harrow should be used 
in order to thoroughly mix the clay and loam and sand 
or gravel. This mixture when found makes an excel- 
lent road, it having many of the elements of the Sand- 
clay Road which is described in Chapter XII. 

After an earth road has been graded and shaped, and 
the fresh earth on the surface evenly and uniformly 
distributed, rolling will add much to its excellence and 
durability. The question of the availability of a steam 
or gasoline roller, and the expense connected with its 
use, has much to do with the economy of rolling an 
earth road, and each community must decide the ques- 
tion for itself. Thousands of townships and other 
municipalities throughout the United States own road 
rollers as a part of their municipal highway equipment; 
in case of a public-owned roller, or where one can be 
secured on reasonable terms, a thorough rolling of the 
earth road will result in an ultimate economy. Even 



182 



PRACTICAL ROAD BUILDING 




^1 



P«H 



rolling with the ordinary farm 
roller, drawn by horses, will be 
a benefit to the road, but not to 
the extent that a heavy rolling 
would be. Whenever earth 
roads are rolled the rolling 
should begin on the sides, and 
continue toward the center, so 
that the top of the rounded 
roadway will be the last to be 
rolled. 

In improving an earth road, 
especially where it is to be 
straightened or other irregu- 
larities of subgrade corrected, 
it is often necessary to use the 
plough. When hard places are 
left in the former road, to be 
covered with different thick- 
nesses of fresh earth, the results 
will not be satisfactory. The 
hard surface must be ploughed 
up to a sufficient depth so that 
the fresh earth, placed upon it, 
will wear down into a compact 
mass. For this reason it is often 
necessary to plough up the entire 



EARTH ROADS 183 

road surface, cutting only as deep as may be necessary 
to get a fairly even foundation, without hard spots or 
soft spots which may later affect the surface. 

The ploughing should be done by back-furrow, throw- 
ing the earth together along the stakes recently men- 
tioned on the center line of the road. Care should be 
taken that each outside furrow reach a trifle lower base 
level than the one before it, so that the hard earth 
forming the subgrade may have a gradual slope toward 
the side ditches. Moisture accumulates more readily 
in newly placed earth than in the harder undisturbed 
ground, and if the hard ground is loosened in such a 
manner as to make a slope from the center each way, the 
moisture in the fresh earth placed on top will have a 
chance to drain away. Otherwise, if the hard ground 
be left higher at the sides than in the central portion of 
the roadway, the hard ground will act as a basin and 
keep the moisture confined in spots, which will permit 
depressions and sometimes holes in the surface. When 
graders or road machines are used, especial care should 
be taken to see that there is no comb or ridge of hard 
earth between the center of the road and the side 
ditch. 

In most kinds of soil, and in the sections of the 
country where the ground freezes from a few inches to 
several feet in depth in winter, grass or weeds should 
not be permitted to grow on the sides of the roadway. 



184 



PRACTICAL ROAD BUILDING 



Exception may be made where the road is on an em- 
bankment across a low or swampy section where the 
earth disintegrates or gives way easily. In such cases 
the formation of a strong sod often holds the earth in 
place and prevents the road-bed from giving way. 
Except in such cases all vegetation should be kept off 
the roadway. 

In the Southern States, where the element of frost 
is not a factor, there are other variations of the above 
principle to be considered. In some sections of the 
state of Florida, where the soil consists largely of a very 
fine sand, and the ground is nearly level, with very slight 
drainage, the earth road is in its best condition when the 
moisture permeates its base, and water stands in the 
side ditches a foot or two below the level of the roadway. 
The explanation of this seeming paradox lies in the fact 
that that particular quality of sand packs hard when 
moist; when it is dry it becomes loose, and wheels 
plough through it instead of going over it. 

This peculiar quality of soil is recognized even by 
the railroads. Over long stretches of territory in 
Florida railway embankments are built 3 or 4 feet 
above the general land level, and the drainage ditches 
along the sides, while duly equipped to carry off sur- 
plus storm water, are so arranged that water will stand 
in the side ditches and keep the base of the embankment 
saturated. The particular quality of sand in the locali- 




185 



186 PRACTICAL ROAD BUILDING 

ties where this practice prevails is not generally found 
in other sections of the country. 

When an earth road is built on an embankment or 
fill, the side slopes should be sodded or sown with grass 
seed so that a sod will form. This will in a large meas- 
ure prevent the slopes from washing in the run-off of 
storm water, and from being damaged by wind and 
other storms. The grass should not be permitted to 
grow up over the edge of the slope into the roadway, as 
that would retard the run-off and cause the water to 
soak into the road. The same rule of growing sod ap- 
plies when the fill is only on one side of the road; and 
it is also a good plan to follow for the outside slope of 
the side ditches, when the road is built in a cut or on 
level ground, and for the up-hill slope on a side hill 
road. 

The proper time of year to improve an earth road is 
the late spring and early summer. The work should not 
be begun on the roadway proper, except where the grade 
or location is changed materially, until after the ground 
has settled — after the frost has gone out; and it should 
not be delayed so that the moisture shall have been 
dried out by the heat of summer. When the fresh earth 
is put on the road, harrowed, pulverized, and shaped 
into the proper crown, it should be moist enough so 
that either rolling or the travel will pack it down into a 
hard, solid mass. 



EARTH ROADS 187 

If the improvement of the road is left until the ground 
is dried out, it will be largely a waste of time and 
money. The travel over it will cause a good deal of 
dust; will wear the surface down into furrow-like dry 
ruts, and when the fall rains come the fresh earth put on 
will be in a condition to absorb and hold the water until 
it is thoroughly saturated and becomes a mass of mud. 
If by chance it should freeze while in that condition, the 
going out of the frost in the spring will leave the road as 
badly in need of repair as though nothing had been done 
to improve it. Water has a remarkable affinity with 
freshly moved earth. 

If, however, the road has been improved early in the 
season, so that the travel of the summer and fall has 
packed the earth down into a solid mass; and if the 
maintenance has been kept up intelligently, the fall 
rains will run into the side ditches, and the frost will 
have no appreciable effect on the road surface. Then, 
when the spring comes again, just a small amount of 
maintenance attention will put the road in first-class 
condition. With even reasonable care an improved 
earth road should be at its best the season following its 
improvement. 

While the subjects of grades and drainage are fully 
treated in Chapters III and IV, there are some features 
which apply especially to earth roads which may be 
described in this connection. 



188 PRACTICAL ROAD BUILDING 

Within reasonable limits, as the grade of the earth 
road increases the crown of the road should flatten. If 
the crown on a level road be 1 inch to the foot between 
the center line of the road and side ditch, f inch will be 
sufficient on a 5 per cent, and \ inch or even less on a 
steeper grade. Common sense must govern under each 
particular condition. The principle involved is to get 
the storm water into the side ditches with the least 
current and the least damage to the road. Under no 
circumstances, however, should the road be flat enough, 
nor should ruts be permitted deep enough, so as to allow 
the water to run down the center of the road. A road 
can be quickly destroyed or badly damaged by the 
rainfall from a single heavy rain storm running down 
over the surface, instead of settling away into the side 
ditches. Water running down a road gathers force as 
it goes, and gains volume the further it flows, until it 
becomes destructive. Diverted into ditches prepared 
for it, the force of the flow is kept off the surface of the 
road. 

In some kinds of earth the bottoms of the side ditches 
will not cut out much even under a heavy flow of water. 
Where the ditch reaches to clay, or hard-pan, or hard 
gravel, or any one of several kinds of hard earth, there 
is little danger; but if the earth be of a nature which will 
wash easily, some solid form of bottom must be provided 
for the ditch on heavy grades. Cobblestones or flat 



EARTH ROADS 189 

stones, laid carefully in the ditch bottom, curving up at 
the edges; or field stones set on edge and the spaces filled 
with smaller stone or gravel, may be used, according to 
whatever material is most convenient. In some cases 
it is desirable to put in concrete ditches if the grade is 
steep enough so that the water will get under those 
made of stone, and the earth has those qualities which 
will make it wash out quickly. 

An important factor is to get the water out of the 
ditch before so great a volume and current have ac- 
cumulated as to cause damage. On most heavy grades 
an outlet can be found on one side of the road or the 
other. In such cases the water from the inside ditch 
should be carried to the outside through culverts at 
distances ranging from 200 to 400 feet, according to the 
grade, and discharged from the right of way, together 
with the water from the outside ditch, into some natu- 
ral channel of drainage. The culverts should be large 
enough to carry all possible accumulation of water, and 
should have pitch enough so that they will keep them- 
selves washed clean of sediment, and carry off the water 
readily, without backing it up at the opening. 

Sometimes, however, it becomes necessary to carry 
the water down a long hill with no chance to get it off 
the right of way until the bottom of the hill is reached. 
In such case the most satisfactory method seems to 
be to lay sewer pipe, or some other large sized pipe 



190 PRACTICAL ROAD BUILDING 

under one of the side ditches, with openings every 200 
or 300 feet, with cross culverts from the other side 
ditch, so that the constantly increasing volume of water 
may be carried off without damage to either the side 
ditches or to the road. 

Under no circumstances should water-breaks be built 
across a road. The water should always be carried 
underneath the road in culverts. These culverts may- 
be made of various forms of galvanized or cast iron, of 
concrete, or of stone, according to conditions. But the 
wooden culvert should not be used except under unusual 
circumstances, as the cost of keeping it up will soon pay 
for a permanent one. 

Summarized, the earth road may be considered as 
involving : 

(1) Width of road and of right of way. 

(2) The crown: its height and position on a straight 
road, on curves, and on side hill roads. 

(3) Alignment, location. 

(4) Preparing the road under different conditions. 
Removal of sod, equipment, and methods. Harrow- 
ing and rolling. 

(5) Exception in certain states where frost is not a 
factor. 

(6) Preparing the side slopes. 

(7) Time of year for improving earth roads. 

(8) Connection of grade and drainage. 






EARTH ROADS 191 

A careful consideration of these factors will make 
possible the construction of earth roads which, with 
proper care, should last for years under any ordinary 
traffic such as earth roads should be expected to stand. 
When the travel becomes so heavy that a good earth 
road goes to pieces under it, ordinary economy demands 
a more substantial surfacing. 

Earth Road Maintenance 

The most approved method of maintaining an earth 
road is by dragging. The dragging should begin as 
soon after the frost is out of the ground as possible, so 
that the earth is dry enough so that mud will not clog 
up under the drag, but will smooth out into a smooth 
surface. The dragging should begin at the sides of 
the road, going one way and returning the other, and 
continue by successive trips until the earth is carried 
to the center of the road, and the crown maintained in 
its original form. 

The dragging should continue until all ruts and deep 
wheel tracks are filled in and smoothed over, so that the 
water will run off into the ditches. After every rain the 
road should be dragged so as to preserve the shape, take 
the water out of ruts which may have formed, and even 
up the surface to a proper shape and crown. In some 
states the law provides for dragging earth roads when- 
ever necessary. Generally this is done by contract 



192 PRACTICAL ROAD BUILDING 

with farmers along the road, each having a certain dis- 
tance to cover, and being compensated, by the mile, 
for each dragging which may be necessary during the 
season. 

There is a variety of road drags, and road hones, and 
road smoothers on the market, some made of wood, 
some of metal, and others of these materials combined. 
All of them seem to serve the same purpose, though 
some of the more elaborate ones have advantages in the 
way of mechanism and cutting facilities which make 
them useful in reshaping the road after it has been dam- 
aged by unusually heavy traffic. Some of these 
machines are so constructed as to take the place of the 
road machine up to a certain point where the road has 
to be reshaped. 

The most common and popular form of drag is what 
is known as the split-log drag. This drag ' is easily 
made by anyone with even an elementary knowledge 
of tools, and its cost is trifling. 

Take a log 8 or 10 inches in diameter, 8 feet long, and 
split or saw it lengthwise in halves. Set the two halves 
with their flat sides facing the same way, about 3 feet 
apart, so placed that one end of each shall extend about 
1| feet beyond the end of the other. Connect the two 
sections of log with two cross-pieces, about 4 feet apart, 
set in solidly either with a mortice or at least a 3-inch 
augur hole. On these cross-pieces fasten a board for the 



EARTH ROADS 193 

driver to stand on whenever it is desirable to give the 
drag extra weight. 

In attaching the hauling chain to the drag it should 
be so adjusted that the drag will be hauled at an angle 
which will throw the earth toward the middle of the 
road, and so that the rear section of log will be directly 
behind the front one. It is usual, in building a split- 
log drag, to spike a strip of old wagon tire or other 
band or strap iron along the bottom or cutting edge of 
the section, especially the front one, which encounters 
most of the obstructions. Similar drags may be made 
of plank by spiking on extra pieces to prevent splitting 
under the strain. 

Constant attention must be given an earth road if it 
is to be kept in good condition. The stones must be 
kept off and the side ditches and culverts kept open. 
Grass or weeds should not be permitted to grow nor 
sod to form on the roadway. Holes must be filled 
promptly with fresh earth. If soft or spongy spots de- 
velop, the soft earth should be dug out and fresh earth 
packed into its place. 

When a mud-hole is found at a low place in the road, 
it is not wise to dump stone into it, then cover the stone 
with earth. Such a course will leave two mud-holes 
idstead of one, one at either end of the pile of stone. 

First, the mud-hole should be drained and some kind 
of a permanent drain left to carry off the water in the 

13 



194 PRACTICAL ROAD BUILDING 

future. Where stone is available a drain of loose stone 
is advisable. Then fresh earth of a quality which will 
pack should be put in and the roadway brought a trifle 
higher than the regular grade, so that when the earth 
becomes thoroughly firm the grade will be even with 
that of the adjacent sections of road. 

With careful attention to details, and the exercise of 
good common sense, an earth road carrying any ordinary 
travel can be kept in good condition the year round 
except, possibly, in some soils, the few days during 
which the frost is leaving the ground, at a very moderate 
expense. But it must be borne in mind that any 
neglect of a road which permits it to get in bad condi- 
tion very materially increases the average cost. 

After an earth road has been put in good condition^ 
the cost of maintenance is comparatively small. Buj 
failure to keep up the maintenance is likely to result in 
as much damage in a single season as proper care would 
cost in five years. 

Earth roads, like all others, require constant and 
intelligent care and attention. 



CHAPTER XI 



GRAVEL ROADS 



Gravel, in some form, is one of the most widely dis- 
tributed road materials in the United States. Deposits 
of gravel are found nearly everywhere, except in the 
alluvial lands in the valleys of rivers and along low sea 
and lake coasts, and in the higher mountain regions. 
The scientific theory is that in one of the subdivisions 
of the Pliocene Age the northern half of the United 
States east of the Rockies was covered with a layer of 
glaciers which came down from the north, carrying 
gravel and other materials, ploughing the surface of 
the country into irregular shapes, and in their melting 
depositing the gravel and clay and stone where the' 
glaciers which held them finally rested. The escape of 
the waters formed by the melting of the glaciers is 
supposed to account for the location of the channels of 
rivers, creeks, and smaller streams as the waters sought 
sea level. 

The scientific theory of the glacial agency in account- 
ing for the presence of gravel is confirmed to a certain 
extent by the fact that certain gravels in some sections 
are plainly identified as particles of certain rocks which 

195 



196 PRACTICAL ROAD BUILDING 

are found in regions far north. But other gravels, in 
localities not supposed to have been affected by the 
glacial movement, may have been the product of a 
previous "Geologic Age," the status of which is not 
well denned. Students who devote their lives to the 
various theories are able, in some instances, to furnish 
practical information. Their researches and the re- 
sults are entitled to respectful consideration. 

Gravel that is found in pits or beds is generally con- 
sidered better for road building purposes than that 
found in the bottoms of creeks or rivers. The reason 
for this is that most pit gravel has a thin coating of 
clayey substance covering each particular particle or 
pebble of which the gravel is composed. Gravel with 
such a coating constitutes what is known as "cementi- 
tious" gravel; that is, gravel which will compact into a 
a firm, solid mass under a road roller or under traffic. 
Gravel taken from the beds of streams does not have 
this coating. It has been washed off by the action of 
water, and the material has become what is known as 
" washed gravel." If a binder is used in building the 
road surface the washed gravel is far superior to the 
"cementitious" gravel. In fact, if a bituminous binder 
is used in a gravel road it is necessary that the gravel 
be clean of coating material. If pit gravel be used it 
must be artificially washed to remove the clay or other 
coating on the particles. 



GRAVEL ROADS 197 

In building a gravel road the earth should be exca- 
vated to a distance of 8 inches below the level of the 
finished road and firm shoulders left at each side. The 
subgrade thus formed should have the same curve or 
crown as the road is expected to have when completed. 
This subgrade should be rolled with a machine roller, 
the heavier the better, and if any soft or springy or 
spongy spots develop under the rolling, the earth should 
be dug out and solid earth which will pack put in its 
place. When wet spots are found they should be pro- 
vided with under drainage. (See Chapter IV.) 

There are two methods of placing the gravel. One is 
to deposit the gravel to a depth of 10 inches and then 
rake the small pebbles to the top, allowing the larger 
ones to be worked to the bottom. Under a roller the 
10 inches of loose gravel will compact to about 8 inches 
in the finished road. It is considered by most practical 
road builders, however, that it is better to lay the gravel 
in two courses. The bottom course should be of the 
larger pebbles, but not larger than 2\ or 3 inches in 
diameter, and not smaller than about 1J inches. This 
course should be laid about 6 inches deep, a little sand 
from the screen spread over it, and rolled to a thickness 
of about 5 inches or perhaps a trifle less. On this 
should be spread 4 inches of properly graded finer gravel 
ranging in size of particles from sand to 1- or lj-inch 
pebbles, and the whole mass rolled to a thickness of 8 



198 PRACTICAL ROAD BUILDING 

inches. In such a road the "pit" or cementitious gravel 
should always be used, and the rolling should be thor- 
ough. The rolling should begin at the sides and work 
toward the center, making a smooth even finish on the 
surface and uniform hardness below. 

The old-time method of dumping gravel on the road- 
way and letting the traffic "wear it down" is neither 
economical nor satisfactory. It is a waste of material, 
and even if the road be in a locality where gravel is 
plenty and cheap the hauling costs money; and such a 
road can never give satisfaction because the larger 
pebbles will always be working to the surface, and the 
road will be rough and uneven. The same amount of 
money, if put into proper construction, will make a 
much more satisfactory road. 

Probably the gravel road has reached its highest 
modern point of excellence in the states of Vermont and 
New Hampshire. These states, with limited means at 
their disposal, have gone forward year by year, putting 
in stretches of gravel and other roads where they- were 
the most needed, until both states have long stretches 
of excellent roads — mostly gravel. 

The maintenance of these gravel roads is simple. It 
consists in spreading a thin layer of fine gravel over the 
surface and rolling it, if a roller be available. If not, 
the traffic will compact it by reason of the fineness of 
the material and the thinness of the layer. In some 



GRAVEL ROADS 



199 




Fig. 19. — A gravel road in New York State. 



sections of the country gravel roads require dragging at 
frequent intervals. This may be due in some cases to 
the nature of the coating or cementing factor in the 



200 PRACTICAL ROAD BUILDING 

gravel itself; or to unusually heavy traffic; or to a travel 
that "tracks" until ruts are produced; or to extremes of 
wet or dry weather. When the winter weather is so 
severe and the drainage so insufficient that the sub- 
grade becomes honeycombed, traffic should be kept off 
the road during the thawing season to prevent its de- 
struction, and the road should be rolled with a heavy 
machine roller as soon as the frost is out of the ground. 
Where uneven places appear more gravel should be 
added to fill depressions until the road surface is smooth 
and even. These conditions are likely to develop in 
but few sections of the country, and only in occasional 
seasons of especially low temperature, or where proper 
attention to drainage has not been given. 

In earlier days Ohio and Indiana built many miles of 
gravel roads as "feeders," or connections, of the old 
National Road. What these states did systematically 
many other states did sectionally. These states each 
built several thousand miles of gravel roads, mostly 
without careful attention to grade or to the other fea- 
tures which modern roads require. These roads, under 
the older conditions of travel and traffic, were an im- 
portant factor in the development of the agricultural 
and other interests of those sections at the time they 
were built. Proper maintenance, however, was in 
most instances neglected, and modern traffic finds a 



GRAVEL ROADS 201 

large percentage of those old gravel roads in a practi- 
cally ruined condition. 

In many instances, however, these old gravel roads 
furnish an excellent foundation for a new road, and 
much money is saved by making use of them. It is 
often found that the dumping of fresh gravel on the 
road from year to year to be packed down by the traffic 
has resulted in a foundation solid enough and deep 
enough to carry any kind of a road surface. In such 
cases the foundation should not be disturbed. The 
surface should be cut down with a scarifier until the 
road has the proper or desired shape, defective places 
filled in and rolled or tamped, and a surface put on of the 
gravel, as described previously. Of course, it may be 
necessary at times, in order to reduce grades, widen 
curves, or for other local reasons, to dig up the old foun- 
dations; but the necessity should be carefully studied 
before such a course is decided upon. 

There is a great variation in the quality of gravels. 
In some the pebbles are round or nearly so. In others 
they are of irregular, angular shapes. The angular 
shape makes a better road, as it compacts better. The 
pebbles of which some gravels are composed are of trap 
rock, others are of different colors of granite, others of 
quartz, and still others of softer stones. What is known 
as "blue" gravel is usually of trap rock and is held by 
most road builders to be the highest grade of gravel for 



202 PRACTICAL ROAD BUILDING 

road purposes; but those of granite and quartz, if hard, 
make good road surfaces. Almost any gravel which 
will pack well makes a good lower, or foundation, course. 

In several of the Southern States a very soft gravel is 
found in liberal quantities. Owing to its softness it 
does not make a durable or satisfactory road surface, 
grinding into dust during dry weather. But it packs 
excellently and makes a first-class foundation for what- 
ever surface the traffic may require. 

In building a gravel road special attention should 
be given to grading the gravel, especially in the surface 
course. The pebbles should be in the proper proportion 
of the various sizes so that the smaller ones will fit into 
the spaces between the larger, and sand enough should 
be added to fill the spaces between the smaller stones. 
When gravel is screened to get the proper proportion 
of sizes the tailings from the screen may be used instead 
of sand, as they usually consist of the clayey or other 
cementing substance forming the coating on the pebbles 
of which the gravel consists. 

Gravel should not be dumped on the roadway before 
spreading. When spreading wagons are available 
their use is an advantage. When they are not available 
the gravel should be spread with shovels from wagons, 
or dumped on boards and spread with shovels, so as to 
make an even surface. Otherwise the road will wear 
unevenly. 



GRAVEL ROADS 203 

When the traffic on a gravel road becomes so heavy 
that the dust becomes a nuisance, it requires a bitumin- 
ous treatment on or in the surface course. This takes 
it into the class of Road Surfaces, and is described in 
Chapter VI. 

In some sections of the country large numbers of 
boulders are found of the same quality of stone as the 
gravel in those localities, and sometimes imbedded in 
the same pit. These boulders are usually very hard. 
They range in size from the gravel up to several feet in 
diameter. Some roads have been built by using such 
of these boulders as range from 3 to about 12 inches in 
diameter as foundations. This is not advised, as the 
irregular character of the foundation will naturally show 
in equally irregular wear on the surface. It is better to 
break up these boulders, crush them in a machine 
crusher, screen the stones into regular sizes, and use 
them as broken stone. Their quality is such that they 
usually make most excellent roads. This method has 
been pursued quite extensively and very successfully 
in parts of Wisconsin, and to a lesser extent in many 
other localities. 



CHAPTER XII 



SAND-CLAY ROADS 



No road offers a greater opportunity for the exercise 
of common sense or "horse sense" in its construction 
than the sand-clay or clay-sand road. This is due to 
the fact that the excellence of the road depends on the 
proper mixing of the clay and sand, and there are so 
many varieties of clay and so much difference in sand, 
even in the same vicinity, that the most careful atten- 
tion is at all times necessary. 

The theory of the sand-clay road is that the sand 
furnishes the body or carrying power of the road, while 
the clay supplies the "sticking'' power which cements 
the particles of sand together, and holds them in a solid 
mass; consequently, the coarser the sand, the more clay 
required to fill the spaces between the particles of sand. 
With very fine sand the amount of clay required is very 
much less. Some road builders suggest the following 
plan for determining the amount or proportion of clay 
necessary in the mixture: 

"Take a measured quantity of the sand to be used — 
say 1 cubic foot or \ cubic foot — have it thoroughly 
dry, and place it in a small tub, or water-tight box, or 

204 



SAND-CLAY ROADS 205 

large bucket. Then put in water slowly, so it will settle 
all through the sand, and come just to the top of the 
sand. Then drain off the water and carefully measure 
its bulk. The amount of water, in bulk, is exactly the 
amount of clay which should be mixed with the sand to 
fill the spaces and stick the particles of sand together. ,, 

While this method will establish the proportions of 
sand and clay to be used, there is so much difference in 
clays that a careful study must be made of them to 
determine their fitness. Not all clays make satisfac- 
tory sand-clay roads. 

Some clays are very sticky and have excellent bind- 
ing power, holding the grains of sand firmly together. 
Others have little or no binding power, due generally to 
particles of mica in the clay, and are almost useless for 
road purposes. Some clays will absorb but little water; 
others are almost like sponge. Some clays will keep 
their shape and sticky qualities for a long time in water; 
others will melt down and dissolve almost immediately 
when submerged in water. 

The clays which are the most sticky and which resist 
the dissolving action of water the most make the best 
roads. The best way to determine whether a clay is 
suitable for road purposes is by actual test. If clay 
sticks to the hands and fingers when they are wet, it is 
likely to be sticky enough for road purposes. If a ball 
of clay holds its shape for a number of hours when im- 



206 PRACTICAL ROAD BUILDING 

mersed in a basin of water, it is likely to hold its position 
when mixed with sand in a road. If it dissolves easily 
it should not be used in road work, as the first rain of 
any considerable duration will dissolve it and leave only 
a sand road. 

Clay from each particular bed or deposit should be 
tested before using, as frequently different qualities of 
clay are found in close proximity to each other. For 
the benefit of those who have the facilities and desire to 
make chemical tests the following technical definition 
of clay is given : 

"Clay consists of hydrated silicate of aluminum, with small 
proportions of the silicates of iron, calcium, magnesium, potas- 
sium, and sodium. Its tenacity and ductility when moist and 
its hardness when dry varies in proportion to the variance in the 
quantities of the materials of which it is composed." 

If clay stands up well in the banks of running streams, 
and does not wash out readily in stream bottoms, it 
should be a good road clay. When it cuts badly it 
should be used with great caution, if used at all, in road 
building. 

In building a sand-clay road on a sand subsoil the 
sand road should first be graded and smoothed, and 
provided with side ditches. Then clay should be ap- 
plied to the top to a thickness of 6 inches and ploughed 
in. At first the plough should not turn up more than 
3 or 4 inches of the sand. Deeper ploughing can follow 




207 



208 PRACTICAL ROAD BUILDING 

if more sand is necessary in the mixture. Then disk 
harrows should be used and water applied so as to first 
completely pulverize and then puddle the mass, after 
which it should be left to dry out, with the traffic kept 
off. This is often a difficult matter, as in certain condi- 
tions of weather it may take some weeks for the sticky 
mass to dry. When it is dry enough it is well to use a 
road roller on it if one be available; in any case, it 
should be trimmed down with a road machine, and 
travel let on by degrees, light vehicles at first, so that the 
surface may be packed gradually. 

When the subsoil is of clay the surface should be 
ploughed to a depth of about 4 inches, thoroughly pul- 
verized, dry, with a disk harrow or with whatever 
utensils will do the work. The clay, in this pulverized 
form, should be left to dry out thoroughly. Then about 
8 inches of clean sand should be placed on top, and mix- 
ing proceed with the disk harrows, or by hand mixing 
with shovels, or by any other means which will secure 
a thorough mixing of the materials. Then water 
should be applied in considerable quantity and the mix- 
ing continued until the mixed mass is saturated. It 
should then be left to dry out, as in the case where the 
clay was placed on the sand, and the subsequent treat- 
ment should be the same. 

Maintenance of sand-clay roads must begin as soon 
as the road is opened to travel. The utmost care in 



SAND-CLAY ROADS 209 

mixing the materials will not always insure a uniform 
surface, and sand or clay must be applied as needed 
until the road wears to a uniform surface. After each 
rain or spell of heavy weather a sand-clay road should 
be gone over and defective places repaired. Often 
dragging with a split-log or other drag is of benefit, with 
the addition of clay or sand as required. 

Practice varies among the advocates and builders of 
sand-clay roads as to the degree of curve or crown which 
such roads should have. Some builders insist that the 
roads, especially when on a sand subsoil, should be 
flat, so that all the moisture except excessive rainfall will 
settle into the sand and add to its firmness. Others 
contend for a high crown, so that the water will run off 
quickly. 

It is probable that the shape, to be of the most value 
to the traffic, should neither be too rounded nor too flat; 
but must depend much on the particular quality of the 
clay in the road. 

North Carolina, South Carolina, and Georgia have 
built sand-clay roads extensively, and in most cases 
they have given excellent satisfaction. There has been 
a wide difference in the cost of these roads, ranging from 
$250 to $2000 a mile, according to the proximity and 
cost of materials, the cost of labor, and other factors. 

Heavy loads on steel tires are reported to be exceed- 
ingly damaging to sand-clay roads. Light buggy travel 

14 



210 



PRACTICAL ROAD BUILDING 



to almost any extent does not seem to injure them, while 
automobile travel, especially on pneumatic tires, is 
stated to be a positive advantage, as the tires keep the 
surface of the road smooth and well and evenly packed. 
In some sections of the country sand and clay are 
found in a natural mixture. Where this appears in 
the roadway all that is necessay is to remove the soil 
covering, and properly grade and drain the road. In 
other cases the soil should be removed to a depth of 
10 or 12 inches and the natural mixture dumped into its 
place and properly shaped, preferably with a road 
machine, and, if possible, rolled with a power roller. 
This natural sand clay should be thoroughly packed 
without the addition of much water, though a little may 
be necessary. 



CHAPTER XIII 



TOP-SOIL ROADS 



As the name indicates, "top-soil" roads are built 
mainly of the surface soil from the fields adjacent to 
the roadway. This soil is placed on the subgrade after 
the road has been properly graded, shaped and drained, 
and prepared for the reception of this material. 

The top-soil roads range in character all the way from 
a sand-clay road to a road of cementitious gravel. The 
top soil which is used for road purposes is composed 
principally of sand, gravel, clay, and a small proportion 
of silt, with some decayed vegetable matter included. 
In the sections where this top soil is found in a proper 
mixture for road purposes the subgrade is usually of 
sand or gravel; or, if there are spots where the sand or 
gravel does not appear, there are gravel pits near 
enough to make a sand-gravel subgrade by a short haul 
of the material. It is held by those who have given 
the top-soil road the most careful study that under 
favorable conditions it is the cheapest and yet the most 
durable and satisfactory road that can be built. 

The top-soil road has reached its highest devel- 
opment, apparently, in the state of Georgia, though 
many miles have been built elsewhere. Reports from 

211 



212 PKACTICAL ROAD BUILDING 

the work in that state are fragmentary by reason of 
the fact that Georgia has no state highway organiza- 
tion, the only practical information obtainable being 
through personal investigation by the author, and occa- 
sional scientific addresses or reports on the subject by 
members of the faculty of the University of Georgia. 

Practical experience has shown that while the sand- 
clay road, described in Chapter XII, requires a careful 
selection of sand and clay for its success, the top-soil 
road may be successful with a wider range of materials, 
amounting at times almost to a reversal of the prin- 
ciples involved. For instance, a clay which would not 
be considered in building a sand-clay road, may pro- 
duce the most satisfactory results when found in a 
natural combination in a surface soil. And silt and 
decayed vegetable matter, which would not be admitted 
in a sand-clay road, become factors of excellence in 
their natural combination in the top soil. These facts 
show that nature can prepare a material which cannot 
be duplicated successfully by man. 

A scientific discussion of this subject is not within 
the province of this book. The fact that the materials 
are available in many sections of the country justifies 
a reference to the Engineering College of the University 
of Georgia for technical information by those who may 
desire it. 

Practically, the top-soil road is a combination of 



TOP-SOIL ROADS 213 

earth, gravel, and sand-clay formed into one, with 
nature performing most or all of the mixing. Where 
the materials are found in the proper proportions the 




Fig. 21. — Top-soil road in Alabama. 

results are very satisfactory; where there is too much 
or too little of any one of the materials, as of clay, or 
sand, or gravel, they may be added, though care must 
be taken not to add too much. 



214 PRACTICAL ROAD BUILDING 

The result, when the proper combination of materials 
is found or prepared, is a good hard road, which pro- 
duces little dust, does not rut under ordinary heavy 
loads, and wears for several seasons with but little main- 
tenance charge. In some cases the road becomes al- 
most as hard as concrete, though not so rigid. At 
times its hardness will resist the cutter of a road ma- 
chine, especially in dry weather. 

In building a top-soil road the top-soil material is 
deposited to a depth of 10 or 12 inches. If the road 
be of a given width the subgrade should be formed by 
excavating, and shoulders made. Either the work 
should be done in wet weather or a reasonable amount 
of water should be applied, so that the material may be 
compacted thoroughly with a roller or with traffic, and 
so distributed that the larger gravel pebbles shall be at 
the bottom. No pebbles larger than 3 inches in diam- 
eter should be allowed in the road. 

So far as is known to the author there are no ex- 
amples of top-soil roads in the Northern or Central 
States. There seems no reason, however, why such 
roads should not be built in any locality where the soil 
and subgrade offer the proper conditions. The ques- 
tions of drainage and protection against frost action 
are practically the same as with earth roads. 

The cost of top-soil roads is given as approximating 
an average of $1200 per mile. 



CHAPTER XIV 

MACADAM ROADS 

"Macadam" is the name applied to almost every 
variety of road the surface of which is made of broken 
stone. How the name of John Louden McAdam, who 
built broken stone roads in England, 1815 to 1824, be- 
came attached to this type of road in the United States 
it is difficult to determine. France had been building 
the same type of roads, instituted by the Engineer 
Tresaguet, for more than sixty years before Mr. 
McAdam became known as a road builder, and had 
constructed more than 15,000 miles of national roads 
under the system. In the United States several hun- 
dred miles of the Old National Road, in some localities 
called the Old Cumberland Road, had been built of 
broken stone in Maryland, Pennsylvania, and Virginia 
before McAdam's construction in the north of England 
became noted. 

Notwithstanding these facts of priority, the name, 
corrupted to "macadam," has been used generally in 
the United States in its application to roads of this 
character. Efforts of scientific organizations to use 

215 



216 PRACTICAL ROAD BUILDING 

another name have failed, so far as the general public is 
concerned. 

Until the automobile became the dominant factor in 
road travel macadam roads were considered the best 
type of roads not only for the country, but also for 
villages, and even for the residence streets in some large 
cities. At the present time macadam without some 
special surfacing is hardly considered for main roads 
in thickly settled communities, and especially where the 
motor traffic is heavy. 

But there are many thousands of miles of road in the 
country where broken stone roads can be economically 
built and maintained. Where the average travel does 
not exceed 250 or 300 vehicles per day, about half auto- 
mobiles and one-quarter heavily loaded wagons on 
steel tires, the macadam road will answer every pur- 
pose. When the traffic gets heavier than that, special 
surfacing should be provided for. 

The width of a macadam road is a matter for local 
judgment in connection with the traffic to be carried 
and the amount of money per mile available. In some 
cases roads have been built only 8 or 9 feet wide. These 
were in sections where the heavy loads are mostly hauled 
in one direction, and a good earth road is usually built 
alongside to accommodate the light travel going the 
other way. Under such circumstances these narrow 
roads have often served a useful purpose. 



MACADAM ROADS 217 

For general team traffic a road should not be less than 
12 feet wide, and where there is automobile travel the 
width should be at least 15 feet; 16 feet is still better, 
as the safety of the vehicles is better provided for and 
the edges of the stone portion of the road are not so 
likely to be damaged by wheels running off and on, and 
grinding along the edge. 

After the proper grade and drainage have been pro- 
vided, as stated in the chapters on those subjects, the 
earth should be excavated to a depth of 8 inches, leaving 
a firm shoulder on each side. The subgrade thus formed 
should have the same shape and crown as the surface 
of the completed road, and should be rolled with a 
heavy machine roller of at least 10 tons' weight. It is 
necessary that the subgrade be packed hard, both for 
the purpose of giving an even support to the road, and 
to prevent the stones from settling or being driven into 
the subgrade. The stone is the most expensive part of 
the road and that which would get into the subgrade 
would be wasted. 

In former years it was the custom to deposit the 
stone in one course. Under modern conditions of 
travel this method has been found unwise and has been 
generally abandoned. Practically all macadam roads 
in recent years have been built in two courses, the 
bottom course about 5 inches thick when rolled, 
and the top course about 3 inches, making 8 inches 




218 




219 



220 



PRACTICAL ROAD BUILDING 



in all. A road built in this manner wears more 
evenly. 

Practically all stone crushers have revolving screens 
which separate the various sizes of stones and deposit 




Fig. 24. — Completed macadam road (New York construction). 



each size in a separate bin. The stones in the lower 
course of a macadam road should range from 1| to 2| 
inches in size and spread 6 inches deep on the subgrade. 
This will compact to about 5 inches under the roller. 
The stone should not be dumped on the subgrade. 



MACADAM ROADS 



221 



£■• ;' •*<* 

.« I» VJ*- s ir • 


f ^3H "^1 * 61 iijr^ 




*-"" "1 /* •*•• Slip 


* ' £ : 11 f J 





Fig. 25. — Macadam road with asphaltic binder (Ohio con- 
struction). 



It should be spread with an automatic spreading wagon 
or spread from the wagons with shovels. If it is neces- 
sary to dump the stone, it should be on dumping boards 



222 PRACTICAL ROAD BUILDING 

and then spread with shovels. No earth or loam or 
sand should be placed on the lower course, nor is it 
necessary to apply any water. The theory of the 
broken stone road is that the stones are so packed to- 
gether as to make a solid structure which will carry 
any reasonable weight which may be placed upon it. 

On this lower course is spread 4 inches of smaller 
stones ranging from J to 1| inches in size. This is 
leveled to the proper shape with rakes, so that the 
smaller stones will be at the top. Then the rolling 
should begin. 

Rolling the top course should begin at the sides, one 
side immediately following the other, with the roller 
extending over the earth shoulder, so as to compress the 
earth and stone together. By doing this the sides of the 
road will be made firm. Then the rolling should con- 
tinue from the sides toward the center. 

As the rolling progresses water should be applied and 
stone chips or screenings spread on the surface. Small 
fragments of stone and stone dust are formed under 
the action of the roller and by the crushing of the edges 
of the stones as they are forced into permanent places. 
These fragments and dust must be washed down into 
the mass by the water and form the cementing binder 
which holds the stones in place. Sand should never 
be used under any circumstances. The water may be 
applied by a hose with a spray nozzle or by a sprink- 



MACADAM ROADS 223 

ling wagon which will deliver the water freely. The 
watering and rolling should go on at the same time and 
continue until the water will no longer settle into the 
road, but will run off at the sides; then the rolling should 
be kept up until the surface is hard, so that the roller 
will not make an impression on it. Then the road is 
ready for traffic. 

While the foregoing description covers the construc- 
tion of a regular two-course macadam road, there are 
several modifications which may be made, especially 
as regards the bottom course, to save expense. 

Naturally, as the wear comes on the top course, the 
stone for this course must be of the best quality ob- 
tainable at anything like a reasonable cost. Almost 
any kind of local stone will answer for a lower or foun- 
dation course. Even coarse gravel is sometimes used, 
with the top course of broken stone; and many of these 
roads have given excellent satisfaction. 

Roads have been built in some localities where traffic 
is light by using 8 or 10 inches of ordinary field stone, 
without crushing, for the lower course. These stones 
were thrown loose into the subgrade, and were broken 
up by men with sledges, so that no stone should be more 
than 8 inches in its largest dimension. Then the mass 
was rolled until every piece of stone found a firm resting 
place, after which the regular macadam top course was 
put on, as previously described. Some of these roads 



224 PRACTICAL ROAD BUILDING 

have worn for several years with good results. They 
cost much less than a regular macadam road. 

Telford is rather the name of a foundation or lower 
course than of a road. The name is that of an engineer 
who built roads in the south of England and in Wales 
at about the same period that McAdam was building 
them in the northern section. In all modern practice 
where Telford's method is used it is as a foundation, 
with a macadam top course. 

In preparing the subgrade for a Telford foundation 
the same method should be followed as for a macadam 
road, except that the excavation should be deeper and 
the subgrade need not be so thoroughly rolled. The 
same care should be given to grade and drainage and to 
having good, substantial shoulders. 

Stones ranging from 6 to 12 inches in length and 2 to 
4 inches in thickness are set up edgewise in courses, 
crosswide of the road. The largest and flattest edge is 
set downward on the subgrade, and the stones placed 
as close together as possible, so that the flat edges cover 
the subgrade as nearly as possible, and so that the 
stones in place may resemble a well-built wall, with the 
face downward, and the irregular points of the stones 
sticking up. Then, with a sledge-hammer, the points 
are broken off, and the pieces driven down between the 
stones to wedge them tight into their places. The 
breaking and wedging of the upstanding points leaves 



MACADAM ROADS 225 

all the stones at about the same height, and the wedging 
makes the structure of the foundation strong enough to 
distribute over a considerable space any weight which 
may come on the road. For this reason the Telford 
foundation is often used in soft and spongy and springy 
soils. In some localities where stone is plenty it has 
been found economical to use it regularly. While more 
expensive than macadam foundations, some veteran 
road builders hold that it will carry a heavy traffic 
as well as a still more expensive one, such as con- 
crete. 

On the Telford foundation is placed the macadam top 
course, as previously described. It is a common cus- 
tom with some road officials to use a regular macadam 
foundation where the subsoil is hard and solid, and to 
put in Telford wherever soft places appear, even a rod 
or so in length. 

The quality of stone in the surface, or top course, is 
of the greatest importance. In many localities stone 
suitable for the bottom or foundation course is found in 
ample quantities, but the surfacing stone must be pur- 
chased and shipped in. Generally the estimates for 
the stone on the road are made by the cubic yard. 
For instance, 1 cubic yard of stone would cover if 
linear yards (a little more than 5§ feet) of 15-foot road 
4 inches thick. But such stone, whether or not pur- 
chased by the cubic yard, always has the freight charges 

15 



226 PRACTICAL ROAD BUILDING 

figured by weight. It is also to be noted that crushed 
stone, shipped in freight cars, will always settle down in 
transit, so that if purchased by the cubic yard it is al- 
ways better to have an understanding as to whether the 
measurement is to be taken at the place of shipment, 
when loaded on the cars, or at the point of delivery, 
before the cars are unloaded. 

The weight of stone varies so greatly that there is no 
given rule that can be applied. The only safe way is 
to weigh a measured cubic yard of the particular stone. 
Some crushed stone weighs but little over a ton per 
cubic yard, while other kinds of stone weigh nearly 1| 
tons. And the weight of the stone is not to be de- 
pended on as a guide to its quality for road surfaces. 
For instance, some crushed granites weigh as low as 
2200 pounds per cubic yard; but granite is so variable 
in quality that it may make an excellent and dur- 
able road surface, or it may wear out in one or two 
seasons. 

On the wearing quality of the surface stone the long 
or short life of the road depends. In some sections of 
the country trap-rock or other high-grade stone is avail- 
able. In other sections, where the stone has to be 
shipped some distance, the cost of freight and the cost of 
the stone from various points must be taken into con- 
sideration, together with tests of the stone for road sur- 
face purposes. 



MACADAM ROADS 227 

The United States Office of Public Roads and Rural 
Engineering, Department of Agriculture, Washington, 
D. C, has a large and well-equipped laboratory for 
testing road materials. The tests are made free of 
charge at the request of any road official. The official 
asking for the test, however, must pay the express 
charges on the samples sent for that purpose. The re- 
port gives the hardness, the toughness, the crushing 
resistance, the binding qualities, and other properties 
of the stone which make for or against its value as 
a road surfacing material. Some state highway de- 
partments and some state universities have similar 
facilities. The use of these facilities to the fullest ex- 
tent is recommended in the selection of stone for the 
top course of macadam roads. On this wearing surface 
depends largely the economy or the waste of money in- 
volved in building the road. 

Many quarries and stone companies which make a 
business of producing stone for road purposes equip 
their salesmen and representatives with copies of 
the government or state official tests of their stone. 
With entirely reliable concerns these reports may be 
depended on. But cases are not unknown where in- 
ferior grades of stone have been supplied, where the 
best was expected. In these cases it is charitable to 
suppose that the stone manufacturer inadvertently per- 
mitted the stone to be shipped without proper examina- 



228 PRACTICAL ROAD BUILDING 

tion or supervision. It is usually safer to guard against 
mistakes of this kind by having tests made when the 
stone arrives, or if previous tests have been made, 
comparing the stone very carefully with the sample 
tested. 

The following figures are rearranged for practical 
application from an elaborate set of tables worked out 
by Mr. R. A. Meeker, State Highway Engineer of New 
Jersey. In that state contracts for macadam roads 
were let on a basis of weight of stone instead of per cubic 
yard, as is the custom in most states. The crushed 
stone used on New Jersey roads weighs from 2350 to 
2500 pounds to the cubic yard. 

SQUARE YARDS IN 1 MILE OF ROAD 

8 feet wide 4,693§ sqjiare yards 

12 " " 7,040 

14 " " 8,213| " 

16 " " 9,386f 

18 " " 10,560 " " 

Any other width can easily be computed from these 
figures. 

The following table contemplates 6 inches of founda- 
tion and 4 inches of surface of loose stone, which will 
compact to 8 inches under proper rolling; and stones 
weighing about 2400 pounds per cubic yard: 



MACADAM ROADS 



229 



STONE REQUIRED PER MILE 



Width of Depth of Amount 




road. 


stone 


per mile. 


8 feet 4 inches 875 tons 


8 ' 


6 ' 


13121 < 




10 ' 


4 ' 


1093| ' 




10 ' 


6 ' 


16401 ' 




12 ' 


4 ' 


1312f ' 




12 < 


6 ' 


1968| ' 




14 ' 


4 ' 


1531| ' 




14 ' 


6 ' 


2296| 




15 ' 


4 ' 


1640f ' 




15 ' 


6 ' 


2460if ' 




16 ' 


4 ' 


1750 




16 ' 


6 ' 


' 2625 




18 ' 


4 ' 


1 1968| ' 




18 ' 


6 ' 


1 2953^ 





With these figures, when the cost of the stone per 
ton, or its cost and weight per cubic yard, is ascertained, 
the cost of the stone per mile for the two courses can be 
easily figured. For any width of road not named, or 
any depth of stone other than those given, the computa- 
tion is one of simple arithmetic. 

In figuring stone by the cubic yard, 1 cubic yard will 
cover 9 square yards of road to a depth of 4 inches, and 
6 square yards to a depth of 6 inches. 



Repairing Macadam Roads 

When a macadam road ravels or when holes develop 
in the surface, the bad place should be cleared of loose 
material and the dust carefully swept out. It is usually 
well to dig a trifle into the edges and bottom of the de- 



230 PRACTICAL ROAD BUILDING 

fective place to be sure of getting to firm material. 
Then fresh stone should be put in, thoroughly watered, 
and tamped or rolled into place. It is not wise to let 
a bad spot develop until it is large enough to call for 
the use of a roller. A tamper, such as is used by pavers 
in cities, should be kept ready for use in repairing the 
smallest defect in the road, and piles of crushed stone 
should be kept within wheelbarrow distance at all 
times. Holes and ravel spots develop very rapidly 
when once the surface is broken and should be repaired 
at the earliest possible moment. 

Maintenance, as distinguished from repair, consists 
of keeping the road surface so protected that the stone 
structure of the road will not wear out or otherwise 
become permanently damaged. This maintenance con- 
sists in sweeping the road surface carefully so that it 
is free from dust and other matter, and spreading about 
J or | inch of fine stone ranging from screenings to f 
inch, or possibly \ inch in size. This may be spread 
over the entire surface or over the worn places, as the 
conditions may suggest, and the work should be done 
at the beginning of the wet season. The traffic will 
then pack the stone into place. Roads have been 
maintained in this manner for many years. 

It must always be borne in mind that the surface of a 
macadam road is to be kept waterproof. Any wear or 
damage, or opening of any kind that will let the water 



MACADAM ROADS 231 

into or through it is likely to cause extensive and ex- 
pensive breaks. 

Bituminous Macadam Roads 

About 1906 and 1907 the growth of the automobile 
traffic on the main roads caused so much wear that 
strenuous efforts were put forth to find a remedy and a 
prevention. Investigation of the subject showed that 
the theory of the macadam or broken stone road would 
not hold under the new conditions. 

The theory of the macadam road, as previously 
stated, is that the particles of stone and dust broken 
from the stones by the steel shoes of horses and the steel 
tires of vehicles are driven into the crevices between 
the stones and, aided by water, form a binder which 
makes the road waterproof and holds the stones in 
place. When the automobile came this was changed. 
The low-bodied, swift-moving vehicle with pneumatic 
tires sucked the binder out from between the stones 
and threw it in the air. Then more steel-shod hoofs 
and steel tires would break down more stone, to be 
thrown off by following automobiles, and the road 
was soon destroyed. 

Experiments by nations and states show that a proper 
bituminous material mixed with the top course of 
stone prevents this extraordinary wear. The situa- 
tion was so grave that International Road Congresses 



232 PRACTICAL ROAD BUILDING 

were held in Paris in 1908, in Brussels in 1910, and in 
London in 1913 to discuss road subjects; primarily the 
protection of the broken stone roads. 

In the use of bituminous materials such as asphalts 
and tars the changes of practice have been numerous 
and rapid. Two methods of applying the bituminous 
material were developed almost from the beginning. 
One was the "penetration" method, and the other the 
"mixing" method. Both have so far been improved 
by modern road builders that only the roads built by 
the penetration method may now be classed as "bitu- 
minous macadam." Roads built by the improvement 
of what was called the "mixing" method are more 
properly classed as "bituminous concrete" and are 
treated in Chapter XVII, under "Bituminous Roads." 

In the use of a bituminous material for binder in a 
macadam road the practice and results have been 
variable. In England the most satisfactory results 
have been obtained by the use of tar. French and 
Spanish road builders have been unable to obtain the 
same degree of success with tars of any kind, but have 
found that asphaltic preparations give the best results. 
In the United States both tar and asphalt have been 
used extensively, both in experiments and in practical 
construction. 

The experience of the last few years seems to show 
that in most sections of this country asphalt has the 



MACADAM ROADS 233 

greater and longer-lived holding power. So promi- 
nently has this fact been demonstrated that in modern 
specifications "bituminous" macadam is rarely named; 
the usual term being "asphaltic" macadam. 

The foundation for an asphaltic macadam road is 
the same as for a macadam road, except that it may 
be a little thicker, to make up for a thinner surface 
course. On the foundation course, before its final 
rolling, should be spread a thin layer of loam or other 
available earth. This is to prevent the asphalt, when 
poured into the surface course, from being wasted by 
dripping down among the foundation stones where it 
would do no good. 

The surfacing stone, ranging from J inch to 1 J inches 
in size, is spread on the foundation course and carefully 
raked over to a depth of 3 inches of loose stone. Some- 
times this is gone over once with a roller to "key" the 
stones in place; that is, to get each particular stone set 
lightly into the place where subsequent rolling will fix it 
firmly. 

On and into this stone is poured lj gallons of hot 
asphalt. The asphalt is usually heated in wheeled 
kettles along the roadside, and the pouring done by 
hand from vessels specially designed for that purpose. 

When the asphalt is applied the stone should be 
thoroughly dry. Closely following the pouring of the 
asphalt, shovelers will spread a thin coat of screenings, 



234 PKACTICAL ROAD BUILDING 

and a heavy roller — at least 10 tons — should be close 
behind. The roller should never be more than 15 to 
30 feet behind the pourers, with the men spreading 
screenings between. 

After rolling, another application of hot asphalt is 
made of i gallon per square yard, and covered with 
f to | inch of screenings. Then the rolling continues 
until the surface is hard and smooth and until the 
heavy roller will make no impression on it. Then the 
road may be opened to traffic. 

Experience in many sections has shown that this last 
i gallon of asphalt and the last coat of screenings form a 
carpet or wearing surface that perfectly protects the 
structure of the road; and that a similar application, 
made once in two or three years, continues the life and 
excellence of the road indefinitely. 

Asphalts for this purpose are of different grades and 
prices. As a general rule the best and most durable 
material costs the most at the point of shipment. 
(See Chapter XVII on Bituminous Roads.) 



CHAPTER XV 



BRICK ROADS 



The general use of brick as a surfacing material for 
country roads is usually confined to those main roads 
where the travel is exceptionally heavy, or where the 
cost, by reason of the nearness of the brick manufactur- 
ing plants, or the absence of other local road materials, 
places it in competition with other types of roads. 
Brick is not a "cheap" road-surfacing material in any 
sense of the term. It is neither low in first cost, nor is 
it subject, if properly constructed, to heavy charges for 
upkeep nor to early destruction. In other words, brick 
roads, when properly built of good brick, while expen- 
sive to begin with, last a long time, cost little to main- 
tain, and give general satisfaction. In all cases, how- 
ever, much care must be exercised in the selection of the 
brick, the preparation of the foundation, and the other 
details of construction. 

Brick roads and pavements were used in Holland 
several hundred years ago, but they do not seem to 
have been in use to any considerable extent elsewhere in 
Europe. A number of isolated cases of brick pavements 

235 



236 PRACTICAL ROAD BUILDING 

in this country at a comparatively early date may prob- 
ably be traced to early Dutch colonists. It is only 
within the last % thirty or forty years that brick has be- 
come a standard paving material in cities, and less than 
half that time since is has been employed to any con- 
siderable extent on country roads. 

Paving brick varies greatly in color, ranging through 
several shades of buff, brown, and red, and some are 
found of a salmon color. The color, however, has 
little or nothing to do with the quality of the brick 
or with its suitability for paving purposes. The bricks 
are made from shales or from fire clays, one or the other 
of which is found in many sections of the country. 
Shales are chemically of the same general composition 
as some kinds of clay; but they have become hardened 
and settled into thin layers something like slate, and 
are found in large deposits. They are made up mostly 
of silica, alumina, oxide or carbonate of iron, with 
traces of lime, magnesia, and other ingredients. Va- 
rious fire clays and some potters' clays of coarse qual- 
ity possess practically the same ingredients; but sur- 
face clays are not often found which will make good 
paving brick. 

Paving brick must be hard, tough, and dense. These 
qualities are produced by having the proper clay, the 
proper mixture, and the proper burning. A lack in any 
one of these three factors may produce a brick which 



BRICK ROADS 237 

has some, but not all, of the three necessary qualifica- 
tions. 

Tests are applied to paving bricks in three ways: 
What is known as the "rattler test," to determine the 
hardness; the "absorption test," to determine the den- 
sity; and the "cross-breaking test," to determine its 
toughness. 

The rattler test consists of putting 10 bricks, which 
have been carefully weighed, into a revolving iron barrel 
specially prepared, and which has been adopted by prac- 
tically all scientific bodies, by many states, and by the 
United States Office of Public Roads and Rural Engi- 
neering as the "standard rattler." With the 10 bricks 
are placed a number of round steel shot 3f inches in 
diameter, weighing about 7J pounds each, and some 
others of one-half that diameter, weighing a trifle less 
than a pound. The barrel is then revolved at the rate 
of about thirty revolutions per minute, one revolution 
in two seconds, until it has had 1800 revolutions. Then 
the bricks are carefully weighed, and the loss in weight 
noted. In some bricks of high quality the loss in weight 
is as low as 16 per cent.; sometimes with a brick which 
looks to be good the loss runs as high as 40 per cent. 
The American Society for Municipal Improvements 
requires that for heavy traffic bricks shall not lose more 
than 22 per cent, in weight in the rattler test; for me- 
dium traffic, 26 per cent. ; and for light traffic, 28 per cent. 



238 PRACTICAL ROAD BUILDING 

Samples for testing should be taken from each carload 
of brick, and should include the softest, the medium, 
and the hardest burned. Generally, if the tests show 
that there are but few soft bricks, the contractor is 
permitted to cull them when unloading from the cars; 
if the proportion of soft bricks is large, the whole carload 
should be rejected. 

The absorption test consists of placing a carefully 
weighed brick in water, letting it soak for forty-eight 
hours, and then weighing it again. This will establish 
the density by figuring the amount of water it has ab- 
sorbed. In sections of the country where freezing 
need not be considered, the amount of water absorbed 
makes little difference. In cold climates, where the 
road surface becomes frozen hard every winter, the less 
water the brick will hold, the longer will be the life of 
the road. 

The cross-breaking test consists in setting a brick 
up edgewise, the same as it is laid in a pavement, on sup- 
ports 6 inches apart, and applying the breaking load in 
the center. Many road builders omit this test if the 
rattler test is satisfactory. 

Bricks for road purposes are usually 3J inches wide, 
8J inches long, and 4 inches high. That is, a brick 
3J x 8| x 4 inches is set on edge crosswise of the road, 
except at road crossings, where they are set diagonally 




239 



240 PRACTICAL ROAD BUILDING 

or cornerwise, so as to present a crosswise front at each 
road approaching the crossing. 

The brick is burned very hard, until it becomes vit- 
rified; that is, given a very hard and usually a glazed 
surface. This burning usually requires seven to ten 
days' time and 1200 to 2000 degrees of heat to secure 
the proper hardness and the right degree of vitrifica- 
tion. Then a period of about as much more time is 
necessary to permit the brick to "anneal" and cool off 
gradually without cracking or other damage. 

Two kinds of road brick are in general use: the 
" wire-cut lug" brick a.nd the "repressed" brick. The 
wire-cut lug bricks are formed by their being cut off 
from the prepared bar of stiff clay by wires running in 
grooves, so that lugs are made on the sides which hold 
the bricks at a proper distance apart to receive the 
filler when they are placed in the road. Repressed 
brick are cut off the bar of clay by an automatic cutter, 
and each brick placed in a die where the corners are 
rounded and the brick is compressed a trifle in size. 
In the repressing some manufacturers leave the name 
or factory mark raised so as to prevent the bricks from 
lying too close together in the roadway, thus serving a 
purpose similar to that of the lugs. 

The general feeling among a large number of road 
builders who have been personally interviewed is that 
the wire-cut lug brick has advantages not possessed by 



BRICK ROADS 241 

the repressed brick, and that it is, therefore, better for 
road purposes. Owing to the keenness of competition, 
however, the subject is a very delicate one, and is 
almost always spoken of as a "personal preference." 
Sometimes one or the other is designated in specifica- 
tions. That the repressing causes a change in the in- 
ternal structure of the bricks is shown by photo- 
graphs of broken bricks printed in a text-book used in 
the Highway Engineering School of Columbia Univer- 
sity (Blanchard and Drowne, p. 554), though points of 
superiority are not pointed out. It is regularly claimed 
that the wire-cut lugs furnish a more even and uniform 
space for filler than can be secured otherwise, and that 
the bricks made by this process have rougher sides, so 
that the filler will stick to the bricks to better advan- 
tage. 

The best brick roads are built on a concrete founda- 
tion 4 to 6 inches in thickness, according to the amount 
of traffic the road is expected to carry. For all ordi- 
nary purposes, and especially if the subgrade be fairly 
solid and uniform, 4 inches of concrete is enough. On 
this concrete is placed a sand cushion lj or 2 inches thick 
which should be rolled with a hand roller, and on this 
sand cushion the bricks are placed, with the hardest 
and best edge upward. The bricks are laid in regular 
courses crosswise of the road and joints broken as in 
ordinary brick masonry. 

16 




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242 



BRICK ROADS 243 

The curb should be of concrete or stone; preferably 
it should be of concrete and be a part of the concrete 
foundation built up at the sides so it will be flush with 
the top of the brick when in place. It is usually the 
custom in laying the brick to place a board, about 
| inch thick, inside the curb when the bricks are laid. 

After the bricks are laid the surface should be swept 
perfectly clean and the surface rolled with a roller 
weighing 3 to 5 tons. This is to settle each brick firmly 
into its bed. Then it is ready for the filler. 

There is much difference of opinion among road build- 
ers as what kind of filler should be used. Formerly 
bituminous materials, as pitch, tar, or asphalt, were gen- 
erally used. These fillers are still used in many sections 
of the country and their use is strongly defended by 
those who favor them. On the other hand, the National 
Paving Brick Manufacturers' Association advocates a 
cement grout filler, made of 1 part Portland cement 
and 1 part sand, mixed into a grout. This method also 
has the support of many competent and experienced 
road builders. 

In applying a bituminous filler the thin board along 
the curb is removed, and the space filled with the tar 
or pitch or asphalt, which has been heated in wheeled 
kettles on the road. Then the hot material is poured 
slowly into the openings between the courses of brick 
from a vessel having a spout especially shaped for the 



244 PRACTICAL ROAD BUILDING 

purpose. If the filler be what is known as "Coal-tar 
Paving Pitch," it should be heated to 300 or 350 degrees; 
if of asphalt the heat should be a trifle greater, perhaps 
reaching 400 degrees. Often with bituminous fillers 
two pourings are desirable, one a few minutes after the 
other, to fill up the spaces to the top of the brick where 
the material from the first pouring had settled down 
further into the crevices between the bricks. Care 
should be taken, in any event, to see that the filling is 
complete, so that both sides and ends of each brick 
are perfectly reached by the filler. 

Expansion joints must be considered when a cement 
grout filler is employed. The space occupied by the 
thin board inside the curb when filled with bituminous 
material provides for the expansion sidewise, whatever 
filler be used. In using a cement grout filler it is the 
general custom to put a similar board crosswise of the 
road every 25 or 50 feet. Many builders, instead of one 
board put about four thin boards, say J inch thick each, 
between courses of brick adjoining each other, so as to 
make a strip about a foot wide across the road to pro- 
vide for expansion by heat and contraction by cold. 

The cement grout filler is mixed in specially prepared 
boxes, which are placed on legs shorter at one end than 
the other, so that the grout may be taken out readily 
with scoops. The mixture, as before stated, should be 
1 : 1 of cement and sand, with the proper amount of 



BRICK ROADS 245 

water to make it run readily. This should be spread 
by scoops over the surface of the bricks and swept into 
the spaces between the bricks with paving brooms. 
This brooming must be done thoroughly, as on the 
perfect filling of all the joints the excellence of the road 
depends. All surplus grout must be swept forward, so 
that the face of the bricks, after the filling has been 
done, shall be clean. 

After the grout has had time to get its first "set," 
but not giving it time to become hard, the boards along 
the curb and those crosswise the road are taken out and 
the spaces filled with a pitch or asphalt filler. If too 
much time is given, and the grout gets thoroughly hard- 
ened, there is likely to be difficulty in getting the boards 
out. 

This form of construction is held by many road build- 
ers to furnish the highest type of brick roads. In- 
stances are known where the ground under such a road 
has been washed out for a distance of 25 or 30 feet, 
leaving the road standing like a bridge, over which 
heavy automobiles passed before the underfilling was 
replaced. 

Concrete foundations for brick roads, where there is 
a reasonably firm subgrade, need not be especially rich. 
A mixture of 1 : 3 : 6 is usually considered sufficient. 
That is, 1 part cement, 3 parts sand, and 6 parts gravel 
or broken stone ranging from \ inch to lj inches in size. 



246 PRACTICAL ROAD BUILDING 

If gravel be used it must be clean, or what is known 
as "washed" gravel. 

Foundations other than concrete have been used ex- 
tensively for brick surfaces. Old macadam and gravel 
roads which have been used for years have been leveled 
down with a scarifier, trimmed to an even grade and 
surfaced with a road machine, curbs put in, and the sand 
cushion and bricks put on in the usual way. Some- 
times a soft gravel of a self-cementing quality has been 
successfully used; and in other instances a very soft 
limestone, such as exists in some sections of the South, 
has been found to make a satisfactory foundation for 
brick roads. 

Ordinary broken stone or gravel such as is used as the 
lower course in macadam roads may be used in sections 
of country where freezing does not extend into the 
foundations of the road. There are also a number of 
special foundations, some of them patented, which are 
worthy of investigation in sections where the materials 
for concrete or other standard foundations are too ex- 
pensive. 

Building brick roads on sand has become a custom 
in some sections of the southern part of the country. 
This custom is perhaps most prevalent in the state of 
Florida, where the subgrade is usually of a very fine 
sand, which packs readily. In building these roads the 
sand foundation is rolled with as heavy a roller as it will 



BRICK ROADS 247 

carry, usually 6 to 10 tons, and the brick placed directly 
on the sand. Formerly the curb consisted of planks 
along the edges held by stakes driven 2 or 3 feet into 
the sand. In later practice concrete curbs are used, set 
about 22 or 24 inches deep and coming flush with the 
brick. Sand is swept into the spaces between the 
bricks and is called by courtesy a "sand filler." 

This type of road cannot be recommended by anyone 
who has a knowledge of the subject and a fair sense of 
values. Owing to long freight hauls brick is expensive. 
The economical use of brick for road surfaces anywhere 
in the country depends largely on the cost of transporta- 
tion. In these particular sections the cost of freights 
alone would pay for a good foundation in some other 
localities. 

While these brick roads "built upon sand" are 
claimed to cost approximately the same as brick roads 
built on a good foundation in other localities, the cost 
of maintenance should practically prohibit their use. 
The torrential rains to which the far southern sections 
are subject drives the water through the so-called sand 
filler, undermines and softens the sand foundation, and 
permits the surface to become uneven and irregular, 
and often results in broken-up places in the surface. 
The annual cost, as a maintenance charge, of taking up 
the bricks, hand-tamping a new sand foundation, and 
relaying the bricks to a good surface, is so great that in 



248 PRACTICAL ROAD BUILDING 

many cases it would pay several times the interest and 
sinking fund on the cost of a good foundation and filler. 
Brick roads, properly built, as designated by those 
who have given the subject the most careful study, are 
among the very best, and, in the long run, economical 
roads that may be found within freight-rate limits. 
Improperly built, they are extravagant and unsatisfac- 
tory and can serve only a temporary purpose. 



Since this chapter was prepared the National Pav- 
ing Brick Manufacturers' Association has begun the 
advocacy of the plan of laying brick in concrete mor- 
tar on a concrete foundation. To do this successfully 
the brick should be laid before the concrete founda- 
tion becomes thoroughly set. Several problems are 
involved, and whether they will work out in actual 
practice remains to be seen. 



CHAPTER XVI 

CONCRETE ROADS 

The use of cement concrete in the construction of 
country roads began to attract general attention about 
1909. Previous to that time many experiments had 
been made, and one or two instances had been observed 
where concrete pavements of twelve to fifteen years' 
duration had been successful. 

The development of concrete roads is shown by the 
fact that while the amount laid in 1909 would amount 
to approximately 40 miles of 15-foot roads, the amount 
laid in 1915 would approximate 215 miles of the same 
width. (The width of 15 feet is used for convenience. 
There are 8800 square yards of 15-foot road per mile.) 

Probably the greatest and most favorable develop- 
ment of concrete roads in the United States has been 
in Wayne County, Michigan, the county in which 
Detroit is located. A considerable mileage has also 
been built in Milwaukee County, Wisconsin, and in a 
number of other sections. 

There are two classes of concrete roads, each of which 
has its supporters. They are the "one course" road, 

249 



250 PRACTICAL ROAD BUILDING 

where the concrete is mixed and laid to the full depth, 
and the road finished in one layer of concrete; and the 
"two course," where one course of a partial thickness of 
the road is first laid and then followed by a second 
course to complete the depth, and on which the finished 
road surface is to be made. 

Advocates of a "one course" road claim that owing 
to the greater mass of material in a solid body cracks are 
less liable to occur, and that the road generally is stronger 
and better; advocates of two courses contend that much 
money may be saved by the use of less cement and a 
poorer grade of stone in the bottom course than is re- 
quired in the top course. Probably localities exist 
where either or both may be correct. 

The grading and drainage for concrete roads do not 
materially differ from those required for other roads, 
and which are treated in chapters on those subjects. 

Forms for concrete roads are very simple. Generally 
they consist of 2j-inch or 3-inch planks of such width 
that when set up edgewise they will come flush with 
the top of the finished road. These planks are held in 
place by stakes driven deeply and firmly into the 
ground. Sometimes metal forms are used, and some 
road builders prefer them as being in the long run more 
economical and more satisfactory in the work. 

The subgrade may either be flat or rounded to corre- 
spond with the shape of the finished road. It is gener- 



CONCRETE ROADS 251 

ally advisable to finish the subgrade after the forms 
have been set, as in this manner a greater evenness can 
be secured with less trouble. When the subgrade is 
flat, the concrete should be thicker in the center than at 
the sides, so as to give the surface the necessary crown. 
However, concrete roads do not require so much crown 
on the surface as most other types of roads. A rounded 
slope of 2 to 3 inches from the center to the sides of a 
16-foot concrete road will answer all purposes of surface 
and flood-water run-off. 

The mixing of concrete for roads is best done in a 
batch mixer with a boom attachment which deposits 
the concrete practically in place on the roadway, where 
it can be quickly and readily raked and tamped and 
the surface evened and smoothed properly. Other 
methods of mixing and placing the concrete are open 
to serious objections. With hand mixing on mixing 
boards it is almost impossible to get the concrete mixed 
evenly and placed on the road quickly enough so as to 
produce satisfactory results. The same is true of the 
work of a machine mixer placed at the roadside and 
delivery made by wheelbarrows. With machine mixers 
with a revolving tube delivery the fine and coarse mate- 
rial in the concrete have a tendency to become separated 
while passing through the tube, and more or less of the 
moisture is likely to drain away. In order to secure 
satisfactory results with concrete in road building the 





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CONCRETE ROADS . 255 

mixing must be done thoroughly and the concrete 
placed on the road wet enough so that the water will 
flush to the top under the tamping; and the material 
must be placed with the greatest regard for the even 
distribution of the large and small and medium-sized 
particles in the concrete aggregate; and it should be done 
within one or two minutes of the time of leaving the 
mixer. A failure to observe any one of these factors 
will result in streaks in the concrete, some of which will 
be weaker than others, and which will be almost certain 
to develop cracks when the road is completed. 

(There are a number of mixing machines on the market with 
the "boom and bucket delivery." Some of them are so ad- 
justed as to move to new positions by their own power; others 
require moving by other means. A road builder can readily de- 
termine which will best suit his purpose by studying the cata- 
logues of the different machines and writing to road officials 
where they have been used.) 

The material should be a first-class Portland cement, 
good, clean, sharp sand, and gravel or broken stone 
ranging from J inch to 1 J inches in size. If gravel be used 
it should be clean of coating or dirt of any kind. What 
is known as "pit gravel" should be washed artificially, 
but that taken from streams is usually clean after being 
screened to size. 

The best proportions of material, according to those 
who have been most successful in building concrete 
roads, are 1 : 1| :3; that is, 1 part cement, lj parts 



256 PRACTICAL ROAD BUILDING 

sand, and 3 parts stone or gravel. Some authorities 
use a little more sand, say If parts, but the general rule 
is 1 : 1| : 3. The materials are placed in the mixer and 
enough water added so as to make a soft mud, and the 
mixing continues until every particle of stone and sand 
is coated by the dissolved cement; then the mixer 
empties it into the bucket, which is run out on the boom 
and dumped as nearly into place as possible. Then 
men with iron rakes rake it into place, and tampers fol- 
low immediately to pack it down into a close, firm mass. 
In the raking care is taken, as far as possible in the lim- 
ited time, to get the larger stones toward the bottom. 
The tamping must show an even firmness, and if solid 
material is lacking in any spot a raker should be called 
back to rake that spot over, and get a better placing of 
the materials. 

The surface, after being tamped, is "struck off" with 
a template, which usually consists of a board with one 
edge cut to the proper curve of the road surface. The 
surface is then usually smoothed with large wooden 
trowels or "floats"; the men doing this smoothing 
working from a plank with blocking under the ends 
resting on the side forms. 

During 1916 a new method of finishing was devel- 
oped. It consists of see-sawing a leather belt across the 
surface at frequent intervals until the surface becomes 
hard. 



CONCRETE ROADS 257 

In "one course" concrete the whole mass is laid to- 
gether and the road practically completed with the 
finishers but a short distance behind those who are 
placing the concrete. 

In "two course" concrete some of the best road build- 
ers use a lower grade of concrete in the bottom course 
and a weaker mixture. Where stone or gravel suitable 
for the surface is expensive, the lower course, which is 
not subjected to wear, may be made of almost any avail- 
able stone or gravel, and a mixture of 1 : 2 : 4 or 1 : 2\ : 
4 used. Usually the lower course is mixed and laid the 
length of the boom on the mixing machine; then the 
materials for the top course are mixed and laid, and the 
surface finished as stated. 

Expansion joints or contraction joints are insisted on 
by most road builders, though there are some that con- 
sider them unnecessary. These joints are placed 20 to 
50 feet apart, according to the judgment of the builder. 
Usually they are made by putting in a board edgewise, 
with tar paper on the sides, the board afterward being 
withdrawn and the space filled with tar or pitch. Some 
builders use soft iron plates to protect the edges of the 
concrete, and fill the space between the plates with pitch 
or tar. There are also some patented joint fillers which 
have been successfully used. The practice on this 
branch of the subject is far from uniform and the re- 
sults variable. 

17 



258 PRACTICAL ROAD BUILDING 

The thickness of a concrete road must be governed 
by the surrounding conditions. The weight of the 
traffic, the character of the subgrade, and the climate 
are important factors. On some heavy traffic roads 
concrete has been laid to a depth of 7 inches at the 
center and 5 inches on the sides with satisfactory re- 
sults. In other cases it has been laid 8 inches and 6 
inches respectively, or on a rounded subgrade 7 inches. 
Two-course concrete is rarely laid less than a total depth 
of 6 inches, the bottom course being from J to 1 inch 
thicker than the top. If the subgrade be sandy or 
easily drained, and the climate be such that there is 
no danger of frost, a thinner concrete may be used than 
where other conditions prevail. Where the center is 
thicker than the sides it has been noted that cracks 
lengthwise of the road are less likely to occur; and where 
freezing reaches into the subgrade cracks are very 
likely to appear when the frost leaves the ground, 
whatever the thickness of the concrete. In some in- 
stances roads as thin as 4 inches have given satisfaction. 
It practically all depends on the local conditions and 
the care which is given to applying the material to meet 
those conditions. 

Covering the concrete road surface with tarpaulin 
should follow as soon as the surface is finished and the 
concrete has its initial set. It is better to wet the tar- 
paulin so as to retard evaporation from the concrete, 



CONCRETE ROADS 259 

which should dry very slowly. After a day or so the 
tarpaulin should be removed, and the concrete surface 
covered with earth to a depth of 2 or 3 inches. This 
earth should be kept sprinkled so as to be moist, but 
not wet, for a period ranging from a week to ten days, 
until the concrete has thoroughly seasoned, after which 
it is swept off. Some road builders admit a certain 
amount of travel during the last two or three days while 
the earth covering remains ; others do not, and consider 
it bad practice. When the earth is removed the road 
may be opened to traffic. 

Cracks are very likely to appear in concrete roads, but 
in many cases and where they are few in number the 
only damage caused is to the appearance. As soon as 
cracks appear they should be filled with tar or paving 
pitch. The cracks are almost invariably due to con- 
traction or to uneven settling; in either case the pitch 
filling, being compressible, is likely to provide room for 
the expansion when it recurs. 

Old macadam or gravel roads should not be given 
concrete surfaces if other materials are available. The 
expansion and contraction of the concrete top, and the 
impossibility of making a perfect joint between the 
new concrete and the old base, and with the liability 
of moisture getting in between, makes such old roads 
more useful for surfaces of greater flexibility. Concrete 
is hard and rigid. To avoid cracks and breaks numer- 



260 PRACTICAL ROAD BUILDING 

ous enough to practically destroy the road the greatest 
care must be taken and every possible condition con- 
sidered. 

Roughening the surface of concrete roads, so as to 
make better holding for horses, is not advocated by 
those who have given the subject the most study. The 
rough surface is said to wear out faster, and it is also 
held that horses soon get used to a smooth pavement of 
any kind so that their hauling capacity — considering 
that the load is on the same smooth surface — is not in 
any way lessened. 

Concrete for roads has its strong advocates and strong 
objectors. Many miles of good concrete roads have 
been built, many other miles have been failures. It is 
claimed, and it is probably true, that those which have 
failed were not built according to the requirements of 
the existing conditions. 



CHAPTER XVII 



BITUMINOUS ROADS 



The general use of bituminous materials in the con- 
struction of country roads, particularly in the United 
States, is of comparatively recent origin. Bituminous 
pavements, such as sheet asphalt and some other forms, 
have been used on city streets since about 1870, and in 
isolated cases some forms of bituminous pavement have 
been reported at a much earlier date. In some Euro- 
pean countries certain "rock asphalts" have been used 
for many years in city streets. 

The development of bituminous roads in this country 
seems to have resulted from the growth of the experi- 
ments with bituminous materials as "dust layers" and 
"road preservatives." When the automobile travel on 
the roads began to reach such proportions that the old- 
time reliable macadam roads were in danger of destruc- 
tion, hundreds of road officials began to experiment in 
the hope of finding a remedy. This was about 1906- 
1907. The first official recognition of the damage 
claimed to be due to the use of automobiles on the 
country roads, so far as noted, is found in the Annual 

261 



262 PRACTICAL ROAD BUILDING 

Report of the Massachusetts Highway Department of 
1907. 

The wide range of these experiments and the pub- 
lication of their results in scientific and other journals; 
their presentation at road conventions and in official 
reports and documents furnished a wide scope for 
study by those responsible for the upkeep of those heavy 
traveled roads which were so rapidly going to pieces. 

From successful use as dust layers it was found that 
bituminous materials, properly applied, made good 
"preservatives." That is, that they could be put on 
the surface of a road, covered with stone screenings, 
and that a sort of carpet thus formed would sustain the 
wear and preserve the road structure indefinitely. 
(This method is described in Chapter VI, on Road 
Surfaces.) 

From this it was a short step to using bituminous 
materials in new construction. First, the distribution 
of tar or asphalt on and into the surface of a new 
macadam road, so as to act as a binder, was found to 
work successfully, and called "bituminous macadam." 
Then the system was elaborated and the stone and 
bituminous material were heated and mixed before 
being placed on the road. These were at first also 
called "bituminous macadam" roads, and were dis- 
tinguished from the earlier types, the names "penetra- 
tion method" and "mixing method" being used. Later 



BITUMINOUS ROADS 263 

practice has resulted in further changing the name of 
the mixing method to "bituminous concrete." (Bi- 
tuminous macadam — penetration method — is treated 
in Chapter XIV, on Macadam Roads.) 

Development of the mixing method, or bituminous 
concrete, soon demonstrated that the same principles 
were involved as in the construction of sheet asphalt 
pavements. About the only essential differences are 
that in the bituminous concrete the mineral aggregate, 
instead of consisting of sand and stone dust, is made of 
stones ranging up to f inch and sometimes larger in 
size. The heating and mixing was done in the same 
manner, by machine based on the same principles, only 
modified so as to handle the coarser material. 

In the late 90's Mr. Fred. J. Warren, of Boston, 
secured a patent on what was named a "bitulithic" 
pavement, which at once entered into competition for 
city streets with sheet asphalt. Mr. Warren subse- 
quently alluded to this mixture as "bituminous con- 
crete," it differing principally from ordinary concrete 
in having a bituminous cement instead of Portland 
cement as a binder. Later a modification of the 
bitulithic pavement which was named "warrenite" 
was prepared for application to country roads. 

In England and in Canada refined tars have been 
used extensively and satisfactorily as the cementing 
ingredient for bituminous concrete. ' In other Euro- 



264 PRACTICAL ROAD BUILDING 

pean countries and in the United States its success has 
not been marked. Within recent years, particularly, 
most of the practice has been with the use of asphalts 
of various grades, so that the term "asphaltic concrete" 
has largely taken the place of the former name. 

In 1909 the state of Rhode Island adopted bitumin- 
ous concrete as a standard type of construction for its 
state highways. Since that time its use has increased 
rapidly, and it is now (1917) considered by most road 
officials to be the highest type of construction applic- 
able to country highways. 

Asphaltic concrete can be laid on any good solid 
foundation. Old macadam and gravel roads when 
properly leveled down with a scarifier and road machine, 
and swept clean and imperfect spots replaced, make 
excellent foundations for asphaltic concrete surfaces. 
A heavy lower course of new macadam or a well-laid 
Telford base may be used. But it must be understood 
and kept in mind that asphaltic concrete is intended, 
primarily, to supply a durable wearing surface, and only 
aids the base and foundation by protecting them from 
injury. It is not supposed to add to the structural or 
weight-carrying strength of the road, though it does so 
to some extent by securing the distribution of the 
weight of the wheel load over more space. 

A concrete base 4 to 6 inches in thickness is the ideal 
base for an asphaltic concrete road. Where the sub- 



BITUMINOUS ROADS 265 

grade is firm and well packed 4 inches is ample. Nearly 
the entire state road system of California, with different 
surfaces to meet local conditions, has a base of 4-inch 
concrete. Of course, where the travel consists prin- 
cipally of very heavy loads, such as 10-, 12-, or 15-ton 
trucks, 5, 6, or even 7 inches of concrete may be neces- 
sary. But such cases are exceptional. 

The concrete mixture for a foundation or lower 
course is usually made of a 1 : 3 : 6 mix. That is, 1 
part cement, 3 parts sand, and 6 parts broken stone or 
gravel. No stone in the concrete should be larger than 
one-half the thickness of the foundation, and in no case 
should exceed 2J inches in diameter. Extremely hard 
stone is not essential, as there is no wear on it; but a 
fairly tough stone which does not break easily is desir- 
able. In some sections of the country where local stone 
is of a poor quality a larger proportion of cement may 
be used, as a 1 : 2\ : 5 or a 1 : 2 : 4 mix. But this is 
not usually necessary. 

In laying the concrete base it is usual to form con- 
crete shoulders at the sides, rising 2, 2|, or 3 inches 
above the concrete base. These shoulders should be a 
part of the concrete mass forming the base, and should 
be of the same height as the asphalt concrete which is 
to form the surface. For all ordinary road purposes 2 
inches are considered sufficient. 

Mixing plants, for the mixing of asphaltic concrete, 



266 PRACTICAL ROAD BUILDING 

are a part of the equipment of practically all large road 
contractors. Sometimes it is considered wise for coun- 
ties or communities to purchase such plants, especially 
if they have a large mileage of roads to construct. As 
a general proposition, however, it is wiser to have as- 
phaltic or other bituminous roads laid by contract. 
One of the reasons for this is that the preparation and 
laying of asphaltic concrete requires experienced and 
capable workman, and practically all of these are in the 
employ of the responsible road contracting companies. 
Besides, contractors give a bond for the maintenance of 
their work for a period of years. Therefore, while it is 
possible for local officials to purchase equipment and 
organize a force of experienced asphalt handlers to do 
the work, it is questionable whether, in actual practice, 
the results for the money expended will be as satisfac- 
tory as though the work be done by contract, and the 
contractor or contracting company held responsible 
for the results. 

The mixing plants may be what is known as "rail- 
road plants," or the more portable outfits which may 
be hauled on wheels. The railroad plants are mounted 
on cars and operated from railroad tracks in railroad 
yards, or side-tracks, convenient or specially laid for 
their use. The nearness of the road to be built and the 
point at which fuel and sand and stone can be re- 
ceived are the determining factors. 




261 



268 



PRACTICAL ROAD BUILDING 



In the heater, which forms part of the outfit, the 
stone and sand, if sand be used, are heated to a tem- 
perature of 200 degrees. The asphalt is heated in an- 




Fig. 32. — Dumping and spreading asphaltic concrete. 

other heater to a temperature ranging from 250 to 350 
degrees, according to the particular quality of the 
asphalt. Under no circumstances must asphalt be 
heated above 400 degrees. 




Fig. 33. — Distributing asphaltic seal coat with machine, instead 

of by brooming. 

269 



270 



PKACTICAL ROAD BUILDING 



The hot stone and sand and asphalt are then fed into 
the mixing machine in the required proportions, and in 
a manner which will secure the most complete and thor- 
ough results. The mixing continues until every particle 
of stone, and sand, and even the finest stone dust is 




Fig. 34. — Covering the seal coat with sand or screenings. 



completely coated with the hot asphalt. Then the 
mixture is taken to the roadway in specially prepared 
wagons or wheelbarrows, according to the distance, 
and deposited on iron dumping-boards, from which it 
is shoveled to the required place on the road. Work- 




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272 PKACTICAL ROAD BUILDING 

men with iron rakes quickly rake it out so as to make a 
mass of the right thickness and density. 

All this must be done while the material is still hot. 
The heavy roller follows the rakers as closely as possible, 
so that the mass becomes compacted while it is still 
hot, and the rolling continues until the road is hard and 
firm. A roller weighing at least 10 tons should be used. 

A seal coat is then applied. This consists of applying 
about \ gallon of hot asphalt per square yard of road, 
sweeping it over and brooming it into the surface of 
the asphaltic concrete so that every crevice, or opening, 
or pore may be filled. On this is spread enough screen- 
ings or coarse sand to take up the surplus asphalt. 
Then the rolling continues until the heavy roller will 
make no further impression, and the surface is smooth 
and perfect. 

For the best results traffic should be kept off the road 
for at least twenty-four hours to give the material time 
to cool. In many cases this is not insisted on; but very 
heavy loads should not use the road for at least a day. 
The stone used in asphaltic concrete should be of the 
best grade obtainable. Even if stone has to be shipped 
in from a considerable distance, it is of importance that 
it be hard and tough and with high power of resistance 
to crushing and to wear. 

The size of the stone used in asphaltic concrete varies 
greatly. Some authorities use stone the largest pieces 



BITUMINOUS ROADS 273 

of which are 1J or 1 J inches in diameter. Others place 
a limit of f or 1 inch in size. From the largest size the 
stone is graded down to about § inch if sand is used, and 
to dust if sand is not used. Some road builders use 
"crusher-run" stone; that is, all the stone from the larg- 
est allowable size down which comes from the crusher. 
This is on the theory that the sizes into which the stone 
was broken in the crushing process are the sizes that 
will best work together into a solid mass when mixed 
with a material which will stick them together. This 
theory may or may not be correct. In practice it may 
work out that way sometimes, and not in others. 

Some road officials of experience consider the crusher- 
run plan uncertain and insist on certain percentages of 
stone of exact sizes, ranging from the largest to the 
smallest, prepared with scientific accuracy. When this 
is done there is a large number of authorities to choose 
from, each having different specifications, and requiring 
tests of different qualities and sizes to determine the 
fitness of the stone to perform the functions required 
of it. There is no question but that the work and finer 
investigations and analysis of these scientific officials 
have brought out the methods of determining what is 
the best practice, and raised the standards of excellence 
in road building. This fact also applies to the studies in 
asphalts used for cementing the stone into an asphaltic 
concrete. 

18 



274 PRACTICAL ROAD BUILDING 

Sand, when used, should range from coarse to fine, 
and be of a quality known as "sharp" sand; that is, 
sand consisting of angular grains. In the mixing and 
rolling each particular particle of stone and sand should 
be completely coated with asphalt, and should be so 
compressed that the particles should wedge in between 
each other and fill up all the spaces, with the asphalt 
acting as the sticking or gluing substance to hold them 
together. 

The proper selection of asphalt and its proper treat- 
ment to form the cement for an asphalt concrete road is 
of the greatest importance and requires the most care- 
ful consideration. 

Asphalts are of two general classes: "Native as- 
phalts," or those which are taken from asphalt lakes or 
natural deposits; and "oil asphalts," sometimes called 
"residual asphalts," which are the base of some classes 
of crude petroleum, and which constitute the residuum 
after the volatile oils, such as naphtha, kerosene, etc., 
and other by-products have been extracted. 

The native asphalts of commerce are the Trinidad 
asphalt, which is taken from the island of Trinidad, be- 
longing to Great Britain, just off the northeast coast of 
South America, and the Bermudez Asphalt, which 
comes from the Republic of Venezuela. 

The Trinidad asphalt lake is 114 acres in extent, and 
is apparently the crater of an old volcano. The sur- 



BITUMINOUS ROADS 275 

face appears as hard as the surrounding earth, and yet 
the material is in constant but imperceptible motion. 
At about 100 feet from land bottom of the asphalt has 
been found at about 135 feet. In the center of the 
deposit it has been found impracticable to drill much 
deeper than that, as the movement of the asphalt bends 
the tubes and makes further progress impossible. 
When asphalt is taken from the surface, making exca- 
vations 3 or 4 feet deep, the depressions will be found 
filled in the course of a few weeks. When the material 
is taken out in large chunks, weighing often 75 to 100 
pounds each, and put in the hold of a ship, it is found to 
have settled into a solid mass by the time it arrives in 
this country. 

Bermudez asphalt is a much softer material. The 
lake from which it is taken in Venezuela is over 1100 
acres in extent and shallow, located in low, flat, marshy 
ground. When taken out the asphalt is about of the 
consistency of a stiff jelly. Loaded into a dump car for 
a few miles' haul to the docks, it settles into a solid mass 
shaped to the car. Arriving in this country it is re- 
moved from the ships by specially prepared dredges. 

The native asphalts are refined by being placed in 
large oblong tanks or vats, heated to a temperature of 
about 400 degrees, and jets of steam driven through the 
molten mass until all the impurities are removed, and 
the asphalt, on being cooled, is ready for the market. 



276 PRACTICAL ROAD BUILDING 

Certain chemical treatment and tests, to produce and 
determine the exact quality and to insure absolute uni- 
formity, are too technical to be of value in Practical 
Road Building. They belong in the domain of applied 
chemistry. 

Oil asphalts, from petroleums, are of different varie- 
ties and classifications. They are generally found in 
Western and Southwestern oils. The Eastern oils, as 
those of Pennsylvania and West Virginia, usually have a 
base of paraffine instead of asphalt. The oils of 
Oklahoma, Texas, California, and other states in that 
section, and of Mexico are heavy with asphalt, some 
of the latter, especially, being claimed to possess so 
much asphalt that the volatile oils are considered the 
by-product, and the asphaltic base the predominant 
one. Such instances, however, if they exist, are ex- 
ceptions; though almost every oil well presents a dif- 
ferent amount of asphalt in its composition. 

Whether or not the degree of heat required in dis- 
tilling the volatile and other products from these oils 
constitutes a permanent injury to the asphalt residue 
is a question for the expert chemists to discuss. Their 
discussions on this and other phases of the subject 
may be found at great length in various published re- 
ports of scientific bodies, technical conventions, and in 
books printed on the subject. Specifications of various 
highway officials of scientific leanings may also be 



BITUMINOUS ROADS 277 

found in plenty; with requirements as to specific grav- 
ity; flash point (the point at which the material will 
take fire); ductility; solubility, and a variety of other 
requirements, most of which differ in the different speci- 
fications. Some of these technical specifications are 
prepared for the purpose of barring out all but one par- 
ticular brand of asphalt; some will admit more than 
one, and others will cover almost any material with a 
fair proportion of asphalt. 

Naturally, every producer of asphalt claims a supe- 
riority for his product in some particular respect. 
While his claim may be absolutely true, it is always 
possible that local conditions and the conditions where 
the particular material was successful are not the same. 
The wearing quality of a road, both as to the smooth- 
ness and evenness of its surface and the length of time 
it will last with no repair or slight repair, is the main 
object in road building; and to the selection of materials, 
asphaltic and mineral, and to securing the best roads 
for the money, should the judgment and energy of road 
officials be directed. 

In the judgment of many practical men who are en- 
gaged in building roads the local officials who are 
authorized to conclude contracts should satisfy them- 
selves by correspondence or by personal examination 
concerning the wearing qualities of the different mate- 
rials as compared with their cost. Then the specifica- 



278 PKACTICAL ROAD BUILDING 

tions under which bids will be received should name the 
particular materials, especially asphaltic materials, and 
separate bids called for on each; so that the compe- 
tition between the different materials should be clearly 
defined; and allow a consideration of bids in which the 
cost and guarantees, in connection with the previous 
records of the materials under similar conditions, may 
be studied before awarding the contract. 

It seems more satisfactory and productive of better 
results if alternative bids specifying "Bermudez," or 
"Texaco," or "Aztec," or "Trinidad," or "California," 
or "Pioneer," or any one of a number of others; or of 
proprietary cements which do not state the ingredients, 
should be received, subject to investigation of past 
performance and cost of construction, with guarantee 
for a certain period. 

In the. record of what has been done with the differ- 
ent materials, some asphalts will show a worn-out sur- 
face at the end of the bonded guarantee period; others 
will show surfaces in good condition, and perhaps last- 
ing for years afterward. These matters must be taken 
into consideration together with the first cost when 
deciding what material to use and what bid to accept. 

Asphaltic concrete roads require little maintenance 
for several years. Attention should be given them at all 
times, just as attention must be given all roads under 
modern conditions of travel. Defective places may ap- 



BITUMINOUS ROADS 279 

pear anywhere, due to faults in construction or to 
peculiarities in traffic. Generally these may be reme- 
died and the road protected by the application of a thin 
coat of heavy asphaltic oil and screenings. After a 
number of years, when the wear becomes great enough 
to be generally noticeable, an application of hot as- 
phaltic oil or liquid asphalt, about J gallon per square 
yard, covered with f or J inch of stone chips or screen- 
ings, will preserve the road. Reapplications will pre- 
serve it indefinitely. 

There can be no question but that the asphaltic con- 
crete road, considering the cost, is the highest type of 
construction for economical country roads except where 
local conditions may especially favor some other mate- 
rial at less cost. 

An asphaltic concrete road, properly built of the 
proper materials, should not in any climate work into 
bunches or waves on the surface. Nor should the bi- 
tuminous material, under the heat of the sun, melt and 
run to the sides of the road. It may become soft 
enough in the heat of the sun so that depressions as 
great as f or even J inch may be made by heavy loads 
on steel tires. But if the asphaltic cement be of the 
proper brand and grade, the surface will restore itself 
to its original position within a few hours. 

With a careful selection of asphalt, based on its pre- 
vious experiences under similar conditions; and of the 



280 PRACTICAL ROAD BUILDING 

stone and sand and other requirements; the authorities 
having in charge the construction of a first class road 
must assume the responsibility for the selection of 
materials and the acceptance of complete bids. (The 
financial phase of this subject is presented in Chapter 
IX, on Road Finance.) 

It seems appropriate to state, in concluding this 
chapter on Bituminous Roads, that certain proprietary 
or patented combinations are alleged to meet certain 
specifications for asphaltic concrete. If such be the 
case, it argues an "inside knowledge" of requirement 
or of performance, or both. All materials and their 
records should be plainly set forth in any specification 
for which bids are asked. 

It must be remembered that the most valuable 
properties of asphalt are its adhesiveness, cohesive- 
ness, and its lasting character. A satisfactory asphalt 
must stick tightly to every particle of stone and sand, 
and continue to stick after years of wear; it must also 
hold itself together — not break, or cleave, or crumble 
with age and service. These are the practical points 
intended to be covered by technical specifications, but 
many- officials consider it wiser to hold the contractors 
responsible both for the material and workmanship 
and the durability of the road as a whole. 



CHAPTER XVIII 



SAND-ASPHALT ROADS 



Roads made of a mixture of sand and asphaltic 
materials are a development of efforts begun about 
1908 to build a road at reasonable cost on the Cape Cod 
peninsula. These efforts might be considered as experi- 
mental, except for the fact that the officials had a defi- 
nite idea in mind as to what could be done, and set 
about to do it. 

It required several years to work out the problem. 
The report of the details may be obtained from the 
Massachusetts Highway Department, Boston, Mass. 
They show the progress, from year to year, of compact- 
ing the subgrade and applying the asphalt. Then 
having the road rutted by traffic and injured by other 
conditions, and smoothed by a drag or a road machine, 
and applying more sand and asphalt; and finally the 
development of a good hard road, suitable for use the 
year round. The information spread, and many local- 
ities have availed themselves of it, with the practice 
modified to meet local conditions. 

One of the contractors engaged on the Cape Cod road 
owned a hotel in a small town in central Florida. He 

281 



282 



PRACTICAL ROAD BUILDING 



decided to build such a road for a distance of 600 feet 
in front of the hotel and on some additional drives 
within the grounds. Equipment and expert workmen 
were taken to Florida from the contractor's home in 




Fig. 36. — Laying sand asphalt near Mt. Doro, Florida. 



Connecticut, and the road was constructed according to 
knowledge gained on the Cape Cod road. 

There were differences to be provided for. The Cape 
Cod sand is mostly rather coarse, Florida sand is very 
fine. The Cape Cod climate produces hard freezing in 
winter. In Florida the frost does not enter the ground. 



SAND -ASPHALT ROADS 



283 



The action of the rays of the sun in the tropical region 
also had to be considered. 

Some years previously a sand-clay road had been 
built on that 600 feet. The clay of that region is easily 




Fig. 37. — Sand-asphalt road near Ocala, Florida. Lime rock 
shoulders not rolled. 



soluble, and the clay had mostly dissolved and the road 
practically gone to pieces. What there was left of it, 
however, was ploughed up, leveled, shaped, and rolled 
hard as a foundation for the asphaltic surface. It is 
proper to state in this connection that in most sections 



284 PRACTICAL ROAD BUILDING 

of the peninsula of Florida the sand which forms the 
subsoil, and sometimes the soil, will, when moist, pack 
very hard under a heavy roller; and will retain that 
firmness for a long time unless exposed to the air or 
to the washing action of water. 

The sand and asphalt were mixed in a portable as- 
phalt mixer, placed on the foundation, and rolled to a 
depth of about 2 J inches. The sand was heated before 
mixing. The mixture was approximately 90 per cent, 
sand and 10 per cent, asphalt, though probably on 
account of it being a "home job" the exact figures were 
not kept. The expert workmen in charge used their 
judgment as to how to make the best and most lasting 
road. 

The road was an entire success; certain large con- 
tracting companies shortly afterward began work on 
considerable stretches of roads, using the same basic 
principle, modified to suit the requirements of different 
locations and conditions. Curbs for these roads are 
usually of concrete and are placed flush with the surface 
of the sand-asphalt. 

While this type of construction is comparatively 
new and may be considered still in the experimental 
stage, there appears no reason to doubt that either in 
the present form or in some development which ex- 
perience will bring, sand-asphalt roads may be con- 
structed which will answer all necessary road purposes 



SAND-ASPHALT ROADS 285 

in certain localities for the time being. The cost is 
low as compared with other types in the sections where 
they are most available; and in most cases where they 
have been built or are in contemplation property values 
do not justify a large expenditure per mile. 

Where a community has limited means and a large 
mileage of roads to improve, for the building up of the 
interests of the people of a sandy section, sand-asphalt, 
properly laid, seems to offer the stepping-stone between 
the sparse valuations and traffic and the heavier de- 
mands which will require a more permanent type when 
the country is better settled, its population and traffic 
multiplied, and its values ample. 



CHAPTER XIX 

SPECIAL SURFACE ROADS 

The growth of interest in road building has been 
such within recent years that many inventions have 
been made — and some of them patented or copyrighted 
— which are intended to produce better surfaces or an 
improvement on existing types of roads, and incident- 
ally make fortunes for their promoters and owners. 
Some of these have been very successful; others have 
scarcely been heard from. A few of them are presented 
here. 

Amiesite 

This surface is the invention of Dr. Amies, and is 
controlled by a company having its general offices at 
Easton, Pa. The peculiarity of this road is that the 
stone is coated with a bituminous material of such a 
character and by such methods that it is friable, and 
may be shipped and hauled and laid cold. The material 
is usually prepared at a central plant in the vicinity of 
the stone quarry from which the stone is taken and 
where it is crushed and screened to the required 
sizes. 

286 




287 



288 PRACTICAL ROAD BUILDING 

The lower course is spread on the prepared founda- 
tion 3 inches deep and rolled once. It consists of 
bitumen-coated stone ranging in size from § inch to 1 J 
inches. On this is placed a layer 1 inch thick of simi- 
lar coated stone of \- to §-inch size and rolled. On the 
surface of the coated material is spread clean sharp sand 
to such a thickness as will fill any spaces between the 
coated stones, and the road is then rolled to a finished 
surface. The rolling of amiesite should be very thor- 
ough to secure the best results, and the roller should 
weigh at least 10 tons. 

Amiesite roads have been laid extensively in New 
Jersey and Eastern Pennsylvania, and have been gener- 
ally satisfactory. The foundation of an amiesite road 
is practically the same as for macadam or bitumin- 
ous roads, the amiesite material forming the wearing 
surface. 

Burnt Clay 

In certain large sections of the Lower Mississippi 
Valley there are extensive deposits of a sedimentary 
clay locally known as "gumbo." This gumbo is 
particularly sticky and plastic when wet, and the 
roads made of it are practically impassable in wet 
weather. 

The United States Office of Public Roads, Depart- 
ment of Agriculture, worked out a method by which the 



SPECIAL SURFACE ROADS 



289 



roads in these sections might be improved. The 
method consists in placing alternate layers of gumbo and 
cord wood on the road, after a system of flues have been 
provided, and then setting the wood on fire. As the wood 




Fig. 39. — Preparing to burn clay for a burnt-clay road in Missis- 
sippi. 



in the four or five layers burns the gumbo is first dried 
and then burned to a clinker. 

As the burning is done on the roadway which has 
already been graded and ditched, it only remains neces- 
sary to use a shallow plow to break up the clinker and 

19 



290 PRACTICAL ROAD BUILDING 

mix in enough of the gumbo of the subgrade to thor- 
oughly stick the pieces of clinker together, then smooth 
off and roll the surface. The result is a smooth, hard 
road which is said to wear fairly well, and to answer all 
practical purposes for rural districts. 

The construction of burnt-clay roads is necessarily 
limited to localities where fuel is plenty and cheap. 
An extended description of the details is published in 
Farmers' Bulletin 311, Department of Agriculture, 
Washington, D. C. 

Hassam 

This type of construction is sometimes known as con- 
crete built by the grouting method. Stones ranging in 
size from lj to 2\ inches are laid on the subgrade and 
rolled to a depth of 4 inches. A grout, composed of 
1 part cement and 3 parts sand, is mixed in a machine 
mixer and applied through a pipe to the surface of the 
stone. The rolling continues while the grout is being 
applied and until all the spaces between the stones are 
filled. 

A top course of 2 inches of smaller sized stone, the 
hardest available, with trap-rock preferred, is treated in 
the same manner except that the grout is mixed 1 part 
cement and 2 parts sand. As a surfacing a thick grout 
consisting of 1 part cement, 1 part sand, and 1 part 
pea-stone is swept over and broomed into the surface 



SPECIAL SURFACE ROADS 291 

until all the spaces are filled and the road is smooth. 
The road should be given several days of "set" before 
opening to travel. 

. Rock Asphalt 

Rock asphalt is a granulated rock which is impreg- 
nated with asphalt, and which, when crushed and 
placed on a road, can be rolled to a smooth, hard sur- 
face. Usually a better result is obtained by heating 
the asphalt before placing. 

Mines of rock asphalt in Germany and Switzerland 
have been used as pavements in some cities of Europe 
for many years. In the United States the material is 
found in Kentucky, Oklahoma, Texas, and California, 
and to a less extent in some other states. In some 
localities it has been used quite extensively, and when 
properly laid has been generally satisfactory. 

One difficulty in the use of rock asphalt is found in 
securing material where the asphalt impregnation is 
uniform; that is, where the stone carries the same per- 
centage of asphalt. Any considerable variation in this 
respect is likely to result, especially under heavy traffic, 
in the wearing of holes in the surface. These are read- 
ily repaired by sweeping the dirt out and putting in 
fresh material heated enough to make it stick and 
tamping it down with a tamper. 

The practical use of rock asphalt is limited to certain 



292 PRACTICAL ROAD BUILDING 

areas in the vicinity of the points of production by the 
cost of freights. 

Some sections of Mexico abound in rock asphalts, 
some of most excellent grades, and several Mexican 
cities are mostly paved with it. It has been stated 
that when Cortez captured the city of Mexico he found 
the streets paved with asphaltic rock taken from the 
surrounding hills. 

Shells 

In several localities along the Atlantic and Gulf 
coasts of the United States more or less satisfactory 
roads are made of shells. In Maryland and in the vi- 
cinity of New Orleans oyster shells are used, utilizing 
the raw shells from the great quantities of oysters 
taken. 

Nearly the same method is employed in making a 
shell road as in a macadam of two courses. The same 
kind of compacted subgrade is required, and the lower 
course is about 5 inches, the top course 3 inches. In 
laying the top course only enough water should be used 
to sprinkle the surface. As a surface coat a layer of 
clean sharp sand about | inch thick is spread and thor- 
oughly rolled in. 

Along some other parts of the coasts are found vast 
deposits of what may be called prehistoric shell. This 
is mixed with sand in the natural deposits, and when 




3 
O 



73 

O 



#2 



O 

• I— I 



293 



294 PRACTICAL ROAD BUILDING 

placed on the road, spread, and rolled to a depth of 
about 5 inches, makes a good road for horse vehicle 
traffic; Under the combined traffic of horse-drawn and 
motor-driven travel it wears rapidly to dust and requires 
such frequent replacement that the upkeep is expensive. 
Any shell road wears into grooves rapidly when the 
travel follows a certain track. Some road officials in 
repairing these roads place loose shell in the grooves, 
which causes the travel to distribute itself over the sur- 
face and wear the road more evenly. The state of 
Maryland has a large mileage of shell roads which are 
reported as economical and satisfactory. 

Other Roads. 

Roads have been made by putting about 6 inches of 
wet wheat straw on an earth road surface, mixing it 
with the earth with a disk harrow, and rolling. The 
same method has been followed with sawdust, in the 
vicinity of lumber mills. With both these materials 
a fresh application is required once or twice a year. 

Slag from blast furnaces when crushed makes an ex- 
cellent substitute for stone where the furnaces are near 
enough to justify its use. The slaty refuse from coal- 
mines after being separated from the coal-dust has been 
used with more or less success in some localities, where 
it seems to effect a favorable chemical combination 



SPECIAL SURFACE ROADS 295 

with the soil, producing a fairly hard and durable sur- 
face. In other soils the attempt has failed. 

Petrolithic roads are made by mixing bituminous 
material with the natural soil. This is done by plough- 
ing up the earth to a depth of about 6 inches, pulver- 
izing it with a cultivator, sprinkling with water, and 
applying about 1 gallon of asphaltic oil per square yard. 
This may be done in one or in two applications. The 
earth and oil are then thoroughly mixed, the road 
shaped with a road machine, and rolled with a roller- 
tamper. In many instances surface coatings of sand 
and small quantities of asphaltic oil are added in one 
or two courses, and rolled in with a smooth roller. 

Concrete cubes 2 inches square, laid on a foundation 
of broken stone with a f-inch sand cushion, have made 
satisfactory roads. The cubes are made by machinery 
and allowed to dry for about three months before being 
placed in the road. 

The number of new roads which have been and are 
constantly being invented precludes the possibility of 
mentioning them all, much less describing the process by 
which they are built. Among them are many failures, 
and undoubtedly some of them will be successful when 
properly adapted to conditions into which they will fit. 

The paramount necessity in the construction of any 
road, of any material, and by any method, is that good 
sense and judgment be exercised. 



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